Purify the Timelines
by starlight1395
Summary: Sans always watched the timelines reset. Because of a freak incident, the timeline was contaminated. A mysterious figure told him he had to go in and destroy the hate, but this timeline was more than contaminated. Everyone was dark, twisted. One by one, Sans must save the Underground, before the Underlord destroys him...but who is the Underlord? UnderFell AU
1. Chapter 1

As much as Sans despised the timelines resetting, there was one thing he didn't actually mind too much. The human had reset again, but Sans had lost track of how many times it had happened.

Although he despised it, he did like watching the timelines reset.

The time flowed backwards, like a river in reverse. He let his finger dip into the liquid time and smiled sadly as the moment rippled and continues its adventure. Each time was a little different, each timeline tinted red or blue or purple or a mix of all the colors.

Sans sighed sadly, watching the happy timeline reverse into something unknown. Something moved in his peripherals, and his head shot up. No one had ever joined him here before. He focused his eyes in the distance, but only finding shadows.

He glanced back at the time line and saw black snaking its way through the colors. His vision snapped back up, and widened dangerously. In the shadows was a figure, a tall figure. It was barely there, the body more shadow than actual being.

The shadow being took a step forward and held out a hand towards Sans, the white limb had a large hole in the palm. Sans wanted to take a step back, but found himself frozen in his spot. The figure took another step forward and the short skeleton was able to make out its face.

A sad smile, a few cracks. They were familiar, in an unfamiliar way. They moved closer yet again and let their own fingers dip into the stream. Instantly, black flooded the colors, disporting the moments and memories.

"What are you-" Sans stopped himself. The figure seemed startled at the spreading darkness. "G-Gaster?"

The name came to Sans like a distant dream, barely making any sense. The figure looked up at him and gave a strange smile. The figure – Gaster - reached his hand out to Sans, as if to touch his face, but more of the blackness dripped into the stream, causing the colors to splash up and spill over the edge in a murky puddle.

"D-don't!" But it was too late. The stream was contaminated. Sans had no idea what that meant, but it couldn't be good. Gaster made a low keening sound and tried to scoop the black from the timeline, only succeeding in making the moments even darker.

"Sans… fix it?" His voice was low and grinding, the familiarity making Sans flinch.

"I… I don't know how!" Sans was sweating, his eyes wide.

"Play… game… yourself." The shadows spoke for Gaster. "Destroy… hate."

The world began to tilt, the indication that the timeline was almost done resetting. Sans frantically looked around, trying to save the timeline.

"Gaster what do I do?" He began to cry a little. The shadow man reached out and smudged his thumb across Sans' forehead. He felt something cold on his skull before the world gave a violent jerk. Sans was thrown to his knees, and his eyesight went dark.

* * *

Sans was kneeling in the snow, the cold not yet chilling his exposed leg bones. He stood shakily, already noticing something majorly wrong. He never woke up in the snow. The world always restarted on the fifth of December. Papyrus always called to him as soon as he woke up, calling him a lazy bones and reminding him to put on a jacket before going out.

But not this time. Sans tried to remember what happened, but it was so vague. He was looking at the timeline, like usual. But this time there were shadows everywhere. Shadows on the walls, shadows in the timelines. There was a growling voice, but no words to connect it to.

Sans brushed the snow from his shorts and tried to figure out where he was. Looking directly behind him, he noticed a large locked door. It was almost identical to the one back in the last timeline, but this one was more worn.

Chips in the stone disfigured the designs almost completely. A large crack ran across one of the sides, and the ground was littered with snow covered debris. As Sans was trying to figure out _why_ the door was so destroyed, it opened slightly.

A small figure slipped from the crack, their sobs echoing through the snow. Sans followed them. He would call it muscle memory, if he had any muscles. His magic stopped them at the gate and turned them around.

"Is that any way to greet a new friend? Turn around and shake my hand." He held his hand out, and the human flinched away violently. Sans retracted his hand just as quickly. The kid was shaking like a leaf, and it wasn't just from the cold.

It was then Sans noticed something else about the child. They had a small growth perched on their shoulder. His eyes narrowed and his magic yanked the lump from their shoulder. The yellow flower floated in the air surrounded by a blue aura. The child cried out and jumped up to reach the monster, but Sans refused to let them be injured.

"Put him down!" Their small voice shocked him. They sounded terrified.

"I won't let him hurt you." They looked even more scared.

"Hurt me? He's my friend!" Sans paused. He glanced up at the glowing flower and saw shocked to see tears coming from his little flower eyes. Reluctantly, Sans lowered the flower back into the child's shoulder. The blue aura disappeared.

"What's going on here?" Sans wasn't buying it.

"I f-fell, and Flowey healed me! And he helped me get past…" They shuddered.

"T-toriel?" They flinched at the name. Something was definitely wrong.

"Yeah…" Sans covered his face with his hands. How had this happened?

"Alright Kiddo. Let's head out, there should be someone up ahead and I don't know how friendly he's going to be." They squeaked a little at his tone but grabbed his hand.

Sans and the kid walked through the bridge to the familiar clearing, but something was wrong. The lamp was smashed, and the sentry booth looked abandoned. A loud cackle sounded in the distance and Sans shoved the kid behind him.

"Come on out. We're not here to cause any trouble." Sans tried to sound relaxed and friendly, but an edge seeped into his voice. He heard a branch crack, and a softer cackle before a tall figure came into view. Sans almost collapsed right there.

"Papyrus?" The figure stopped walking for a second. He seemed…. Scared?

"B-brother?" Sans had never heard that amount of terror in his brother's voice before, and he hated it more than anything. He took a step towards his brother and finally saw him. He was the same height, maybe an inch taller, but somehow even skinnier. His Battle Body suit was pitch black and beaten up. The worst thing, however, was the crack covering this entire right eye.

"Pap…" Sans left the child and ran at his brother, _needing_ to make sure he's okay. This Papyrus scrambled back and fell on his tailbone, causing Sans to stop dead in his tracks.

"L-look Brother… I'm so s-sorry I w-wasn't at my post. P-please give me another chance! I can p-prove it to you!" Sans stared at Papyrus with wide, frightened eyes. Even the human realized something was wrong.

"Papyrus… what's going on here?" Sans' voice was soft. He knew this wasn't _his_ Papyrus, but he wanted to pretend for at least one second. Papyrus just gave him a confused look.

"I just… Brother are you alright?"

"Am I alright? Bro look at you! You fell in the snow!" Sans let his voice raise, and he realized a second too late what a mistake that was. Papyrus flinched violently and tried to move back even more. He was trembling. Papyrus was _trembling… because of Sans._

 _"_ B-but… you threatened to… You promised I would regret slacking off again. That it would be even worse than … last time." Papyrus' voice cracked in fear.

Sans made it to his brother's side in two strides and fell to his knees next to him. With trembling hands, he reached out and barely brushed Pap's cheekbone. Papyrus was trembling even harder, his eye clenched shut in fear.

With a cry, Sans wrapped his arms around Papyrus' shoulders. He buried his face in his brother's shoulders and let only a few stray tears escape. Papyrus was frozen under his touch, afraid to move. After a few moments, the gloved hand reached up and patted Sans on the back twice.

"Who…who are you?" Papyrus sounded broken.

"It's me… Sans?" Sans stood and looked at his brother again. "God this is so messed up…"

"You are not my brother. My brother is…" Sans had turned away to face the kid, who had been standing silently behind them.

"Probably not very nice." Sans finished the sentence, not bothering to turn around.

"Is that… a human?" Sans froze, knowing that tone of voice. He heard the other skeleton stand and the telltale hiss of magic. Glancing behind him, Sans saw Papyrus with two dark blue bones in his hands. His good eye was narrowed.

Sans did what he knew he had to do. He summoned his own bone and blocked Papyrus' way. Papyrus stopped dead and stared at the bones with shock and…. Something akin to awe.

"Blue?"

"Bro you're gonna leave the kid alone, or you're gonna have to go through me." Papyrus ripped his eyes away from Sans' magic and stared straight through Sans.

" _What_ are you?" Sans dropped his magic and held a hand out for his brother.

"Papyrus… we need your help. Something is wrong here, and I have to fix it." Papyrus hesitated before slowly reaching out and taking Sans' outstretched hand.

"Sans… what is going on here?"

"It's a long story bro…"

* * *

"We are…wrong?" Papyrus was trying to understand everything Sans just told him, but was having a really hard time.

"Essentially…" Papyrus scratched the crack over his eye and sighed.

"We need to find Undyne." Sans instinctually stepped in front of the child and their flower companion.

"Will she attack the human?" Papyrus' eye opened with slight shock.

"What? No! Undyne is the leader of the rebellion." It was the Sans' turn to widen his eyes in shock. _Rebellion?_ What kind of world did he end up in?

"The _what?"_ Sans was not sure what he wanted to hear.

"Erm… maybe it would be best if Undyne explained it herself." Sans nodded, wanting to get this adventure – or nightmare rather – on a role. Papyrus moved from behind the sentry station, where they were huddled to avoid the cold while Sans told his story. Papyrus pulled out a sleek black phone and hit a single button before holding it up to his skull. Sans turned back to the human and asked something that had been bugging him.

"So kid… what happened to you in the ruins?" The child grimaced a little, and the flower was the one that answered.

"The lady there… she was pretty nice at first, but said she had to take the human's soul before the monster king did. She said she would make it painless… that it had to be done. She didn't seem like she wanted to though…"

Sans connected what dots he had. It seems like this timeline was fundamentally the same, but something happened to change each of the monsters. Toriel must have needed to take the soul before the King, but why?

Papyrus slipped the phone back into his pants and waked over to the two monsters and the human.

"Undyne is thankfully in the area. She told us to make it to her home as discreetly as possible. If we go around Grillby's and make it to the River Person, they should be able to-"

"Don't stress bro. I got this." Sans grabbed hold of the Human's right hand and his brother's left hand before letting his eye glow blue. Papyrus breathed in sharply and muttered _blue again_.

Sans let the magic pulse though him and felt it flare across his surface. The human gasped a little and he let the magic snap. The world went dark, and when the world came back into focus they were standing on the doorstep of a fish shaped house.

Papyrus ripped his hand from Sans' and stumbled to the side, on hand steadying himself on the house and the other grasping his chest. He retched once and breathed heavily for a few moments. His breathing didn't calm, and Sans began to worry.

Just as the shorter skeleton was going to place a hand on his brother's back, the front door flew open. Sans found a spear in his face and a shiny arm wrapped around his brother.

"Step away…" She all but growled at him. "Papyrus you never said _he_ was with you. You've ruined the whole rebellion!" Papyrus was still breathing heavily, but it had calmed down a little bit.

"W-wait Undyne. It's not him." Undyne spun to face Sans, her good eye burning with rage.

"Not him? Are you crazy?" Papyrus stood up straight and ran a hand over his skull shakily.

"Take a closer look." Undyne stepped closer and Sans felt himself tense up. He tried to keep his smile innocent, but he could feel the edges of it trembling. A cold, gloved finger rapped his teeth and he opened his mouth in shock. Undyne's finger tested his fang and as soon as the digit invaded his mouth, it was gone.

"Papyrus. _Explain._ " He gestured to the front door with his head and she nodded. The two of them ushered everyone inside and Undyne locked the door directly behind them. She stared at Sans and the human until they sat at the kitchen table. She slammed her hands down on the table, causing the crack down the middle to grow. "It's obviously not _him._ This one's teeth aren't sharp enough, and his magic is blue. I saw when you guys got here…"

"This is not my brother, you are right. This is some… over version of him. Apparently the timeline he came from is much nicer that this one. Something happened during something called the Reset, causing the timeline to be contaminated."

"You." Undyne got Sans' attention. "Is this true?"

"Yeah Undyne. There's something seriously messed up here, and I have to fix it to get everyone back to normal."

"W-what's… 'normal' for us?" Undyne's voice was timid, afraid of what Sans would say.

"Well… my brother is a little goofy. He doesn't understand how the world really works, but he cares about everyone so much he's willing to try anything. Undyne is headstrong. She honestly believed in taking the soul of the human, because she wanted to free the monsters from the underground. She was adamant about capturing Frisk, but they befriended her and she became a good friend. She was the one who taught Pap how to cook, and had a big ol' crush on Alphys even if she refused to admit it. Alphys was a little awkward, and a lot of nervous, but she helped the human though all the puzzles and really saved their life.

"Toriel lived in the ruins and tried to prevent any humans from leaving so she could protect them from Asgore. The King was always a pushover, but he had to take the human souls to break the barrier, even though he hated violence. Mettaton just wanted to be a star. He tried to take the human soul too, but he realized he was needed in the underground more.

"On the other hand, Flowey was evil. He tried to kill Frisk as soon as they fell down. He followed them and tried to kill them in the end, which explains why I was so harsh when I first saw him on your shoulder."

Everyone was silent. No one knew what to say…

"Well… that time line sound much better than this one." Undyne had taken off her armor and rested her elbows on the table and her face in her hands.

"Now you have to tell me something." She looked up at Sans and didn't like the grin look on his face. "My bro said something about a rebellion. Now, something about that sounds weird."

"I-it's… it's a rebellion against…" She closed her eyes. "Against you Sans."

"Y-you gotta me kiddin me…" Sans wished with every fiber of his being that she was joking, but by the look on her face it was obvious.

"I wish I was. You- the other Sans realized just how powerful a human soul is, and challenged Asgore… and won. He could have gone through the barrier, but he wanted to make sure everyone followed him blindly, so he could lead an army through.

"He ordered me to slaughter any monster that didn't follow him, but I couldn't. I faked my death and started a rebellion against him. Papyrus was the second to join the rebellion, when he was ordered to do what I was, but he stayed as a mole in the inner circle." She growled, but not at either of the skeletons. "I've told him to get out of there, that it's too dangerous now, but he refuses."

"Undyne you know why I stay." Papyrus wasn't happy.

"Yeah and I think it's dumb…"

"Undyne…" Papyrus growled at her in a very not papyrus-like way. She shied away from his tone.

"What are we going to do?" The human hadn't said anything during the talk, so their question caused everyone to jump a little.

"We have to face me… Sans… but we can't go in alone." Papyrus and Undyne exchanged a look and shook their heads.

"Not possible. There's no one in the Underground left to rebel. They've all conformed… or turned to dust."

"What about Alphys? She was always for the greater good." Undyne stood with a violent jerk and walked to the sink. She wiped down the counter and wrung the towel in her hands.

"Alphys… She's not going to help us." Sans was confused.

"Why not? Was she dusted?" The thought sent a pang through his chest. Undyne shook her head sadly. She turned around and pulled off her eye patch. Where her shining black eye should have been was a mass of scar tissue. The hole was ragged and painful looking, despite it being and obviously old wound.

"If only she was dusted… no. She was Sans' number one supporter, but she never told me. I went to her when I was going to fake my death, thinking she would help me. Boy was I wrong." Undyne grimaced and replaced her eye patch. "She attacked me, yelling at me for abandoning the new age of monster kind. She cursed me for abandoning her. She ripped my eye out, and I just barely escaped. The reason Sans accepted the story of my death so easily was because Alphys presented my eye as proof… That traitor…"

Sans clenched his fist on the table and let out a low groan. How was he going to fix this?

"There is one person who might help us…" Papyrus wasn't sitting. He had been standing by the window the whole time, watching out for anyone who might be coming up the way. Everyone turned to him with hopeful eyes, except for one.

"Papyrus no. There's no way he'll-"

"We have to pay a visit to Mettaton."

* * *

 **I adore every single AU Undertale has to offer, and I was reading a story by FlightyFelon and just** ** _adored_** **their Underfell headcannon. I just had to write something myself.**

 **I know I'm in the middle of another Undertale story, but I'm not abandoning it!** ** _Love Yourself_** **will continue, but I just needed a change of scenery.**

 **Thank you everyone for reading! I hope you enjoyed it, and I hope to have the second chapter up before the end of the week!**

 **Until next time!  
~Starlight **


	2. Chapter 2

Sans felt his eyes water at the sight before him. Mettaton's hotel-apartment complex was in shambles. The windows were boarded, the fountain dry as a bone. Dust covered the rugs and the counters. The footsteps of the group echoed painfully loud.

"He's not here Papyrus. No one's seen him in months." The tall dark skeleton was in the lead of the party, but he was sure the robot would be here.

"Exactly. And this place has been closed down for months. Where else would he be? Definitely not the lab."

"Pap…" Sans didn't want to believe what he was seeing. "W-what happened here?"

"It was soon after my brother came to power. He gave Mettaton a strict set of rules for his performances, and he refused. Mettaton always said his performance was more important than anything else…" Papyrus seemed to be somewhere else for a moment before continuing. "Let's just say my brother was no please with Mettaton's disobedience and punished him as he saw fit… no one's seen him since then."

"But what happened to Mettaton to make him go into hiding?" The human wasn't very good at picking up on social hints.

"No one is quite sure child… all we know is that it was inhumane and vile." Papyrus spit the last words out, visibly trembling at the thought of the robot being tortured. The human curled into themselves a little and Flowey placed a leaf on their cheek as a comforting gesture.

"Should we split up?" Undyne had regained her authoritative air, but she was smart enough to know she wasn't in charge of this mission.

"No. It is too dangerous, especially for Sans and the human. We must stay together, no matter how long it takes." Sans let out a breath be hadn't realized he had been holding. He was afraid of splitting up.

"Let's check the rooms first. He might have taken over one as his hideout." Everyone nodded and headed to the elevator. They went up to the first floor. Between Papyrus and Sans' powers, they had no trouble unlocking the doors, but there was no sign of life anywhere.

All the rooms were as they were left, all those months ago. Some had bags and suitcases, covered in a thick layer of dust. A handful had small piles of ash in different places, some on the bed, some by the door – trying to escape. Sans wouldn't let the human near those rooms.

It took almost three hours to check all the rooms, but all they had to show were some very frustrated monsters and a very tired human. They found themselves back in the lobby, and the silence was as deafening as always.

Suddenly there was a sharp crack from the room to their left. The Restaurant? Another loud crack. Papyrus and Sans pushed everyone behind them and walked towards the door slowly and carefully. Papyrus pushed the door open with a tentative hand.

The room was pitch black, but a hole in the ceiling acted as a natural spotlight on the stage. There was a faint light around the stage, and they could see the tables were destroyed, broken in half or flipped upside down. The tablecloths were ripped and stained, with what no one wanted to even guess. The dust particles floated lazily through the light, and a lone figure was collapsed on the stage in a broken looking pile.

Another crack came from the stage, but it wasn't a crack. Two metal hands came together causing a snapping to fill the stagnant air. The bundle began to twist and quiver, but no one moved. The bundle tried to stand, but collapsed back. NO one dared to move.

Papyrus was the first to break the spell and rushed to the stage, his hardened exterior cracking with every step. He stopped mere inches from the stage.

"M-mettaton?" The figure on the stage lurched violently, causing the tall skeleton to take a fraction of a step back. "Mettaton is that you?"

His voice was trembling, but not with fear. With something far more dangerous.

Hope.

The figure lifted something, but Sans couldn't make out what. From his angle, it was a knot of metal and rust. The light shifted a little as a piece of wood snapped from the rafters and fell to the ground with a thump, disturbing the dust.

It was a head, Sans realized. And it was _Mettaton?_ Sans felt his chest constrict painfully. Out of all the twisted monsters in this timeline, _this_ was the most horrific thing Sans had seen.

That _thing_ wasn't Mettaton anymore. Papyrus knew that, but he still knelt next to him and placed a gloved hand on the robot's cheek. His hair was the same as usual, other than the rust covering most of it.

His face was distorted with an extra set of eyes placed right under the first pair. The second pair were pitch black, no iris or pupil to be seen. There were obvious welding marks along his face where the second pair was added on. His mouth had obvious welding marks as well, and when his jaw creaked open everyone saw how sharp his teeth were.

"P…pap…yrus?" His voice sounded like the old gramophone Sans found in the dump one time, grainy and far away. Papyrus jerked when Mettaton recognized him, dark blue tears welling up in his good eye. A metallic hand snaked from the pile of wires, the usually gleaming metal tarnished and rusted. The hand squirmed in the air for a moment before landing gently on the skeleton's face, right on the crack over his eye.

"Yes it is I, dear Mettaton…" Papyrus leaned into Mettaton's touch. "I've missed- We are here to help you."

The robot pile made a whirling sound and Sans took a step forward ready to pull his brother out of the way if need be, but his concern was unnecessary. Mettaton's mouth curved up into a painful smile and a red tear worked its way from the top set of eyes.

"I…am… tan…gled…" His gravelly voice bounced painfully off the walls.

"I can see that. We will help you untangle, so be patient." Mettaton closed his jaw and smiled again, the hinges creaking with disuse.

"Th…ank…you…" His jaw was closed but his gramophone words oozed from the speaker on his chest.

"Brother, Undyne. I need to you help with his arms. Human…" Papyrus hesitated and unwrapped his cape from around his neck. "Human, take this and try to shine him up a little…"

Everyone went to work instantly. Sans and Papyrus using their powers over gravity to gently lift and move the limbs. It became glaringly obvious the second set of eyes wasn't the only modification made. Mettaton had two sets of arms as well, all four limbs ensnared in each other. Many of the points where the arms were touching had developed a layer of rust.

Sans cursed under his breath, realizing that Mettaton had to have been in this position for a very long time, without moving. Papyrus realized the same thing because he looked at the shorter skeleton for affirmation.

"This must be how they dropped him off here…" Sans' voice was uncharacteristically somber. Papyrus clenched his jaw and went back to work. It was tedious to say the least, but eventually it was complete. The human had done a good job of shining him up as best as they could. There was nothing to do about the rust at the moment, but most of the smudges and dust was gone.

Mettaton was sitting up, mostly by himself. He was leaning on Papyrus shoulder slightly, but he looked more like the Mettaton Sans knew.

Sort of.

His usually vibrant pink and black paint was chipped and dull. The rust in his hair made it look like he had highlights put in. His four hands rested in his lap, and his four eyes were closed. He couldn't breathe, the same as Sans and Papyrus, but he mimicked the motions perfectly.

The worst part, more horrifying than all of that combined, were the wending marks covering almost every inch of his body. It was like he was taken apart and put back together again two dozen separate times. Sans scanned the robot, to see if there was an external damaged, when his noticed something that made him double over and retch.

Mettaton's soul was gone.

* * *

 **Short update, but I thought this was the most impactful way to end it. I'll begin the next chapter sometime tonight, and probably post it in the next few days.**

 **Until next time!**

 **~Starlight**


	3. Chapter 3

Sans wasn't in shock. He wasn't stunned or mildly disgusted.

He was shaken right to his core.

Where the glowing pink soul used to be was now a mass of blackened metal. It looked painful no doubt, and Sans could only guess what happened to make such a scar.

"Hey Mettaton… feelin' better?" He kept his voice soft and calm, not wanting to startle the poor creature next to Papyrus.

"Much… better… thank… you." His speech pattern was a little smoother, but shill sounded faint and grainy.

"Do you need anything?" The human was more than willing to help in any way they could.

"Battery…?" Sans could have face palmed. Of course he was out of power…

"Hold on pal. The kid and I'll go search the place for some power." Mettaton opened his top set of eyes a fraction.

"Thank… you… Sans…" Sans stopped in his tracks. If Mettaton remembered what happened to him, he would remember _who_ did it to him, but he didn't seem afraid of this Sans.

The skeleton and the human (and the flower) all left the dark room and stopped at the fountain, none of them having any clue where to start their search. The human's stomach grumbled, and he remembered the Glamburger stand directly north of where they were.

"Come on kid. There might be something to salvage there." Sans tried to open the door, but found it held shut by something. He squared his shoulders and gave it a particularly strong shove, moving whatever was holding the door shut away.

Someone had barricaded the door with boxes, but judging by the pile of ash in the corner, it didn't do them much good. Sans remembered the poor sap that worked behind this very counter and felt a little nauseous. He slid a box over the ashes before the human saw.

They rummaged through some of the boxes, but the only thing they found was crumbs and napkins. Sans glanced at the other door and found it to be a freezer. The freezer was almost completely bare, except for a half-eaten box of bicicles.

"Hey kid, will this work?" It was obvious it wasn't what they were hoping for, but it was better than nothing. While the kid licked at the treat, Sans looked around for some kind of generator or battery or something.

There, tucked behind a pile of cardboard boxes, was a smallish container, about the size of a cooked turkey. It was black, with pink designs around it. There was an old note on top, the writing almost completely faded.

 _Dear Burgerpants~ please keep this behind here just in case!_ It was signed with a heart, and Sans knew exactly what it was.

"Come on kid! We found what we were looking for!" They made their way out of the burger place and back into the lobby. The air was still stagnant, but something made Sans' chest constrict with worry. He glanced around and tried to see if anything was out of place.

The fountain had an unbroken layer of dust, as did the carpet, except where they walked. There were six distinctive sets of footprints in the dust. Sans felt that same constricting in his chest, and for the first time realized he had never felt that before coming to this timeline.

If he didn't know any better, he would say someone was trying to warn him of something.

Sans did a quick headcount of the group and froze. He sprinted to the restaurant, almost forgetting about the kid behind him. They threw the door open and ran to the stage. Sans threw the battery at Papyrus.

"Hook him up and grab him. We're not alone here. We have to get out _now."_ The reaction was immediate. Everyone began scrambling. Papyrus picked Mettaton up and holding him close to his chest and juggled the battery in his fingers. Sans grabbed the human by the wrist and pulled them aside.

He realized he would never be able to take everyone at once. He called to his brother and in three words told him the plan and flashed from the hotel. Sans tossed the human into a show poff and flashed back to get Undyne. It took another second to flash her back to her house.

Sans flashed back one last time to get his brother and felt the constriction in his chest. Something bad was going to happen. He made it back to the stage, only to find the room empty. His knees gave out for a second and he cried out,

"Papyrus?" His voice echoed through the room. Sans felt a bead of sweat slip down his skull and he tried again. "P-papyrus?"

Nothing. Sans jumped from the stage and ran to the lobby. A figure ducked behind the fountain, and Sans needed to make sure his brother was safe. He used his power to freeze the figure and lifted them into the air.

It was the monster child from Snowdin, Sans realized with a start. They were almost exactly the same as the one from his timeline, the only difference was a large scar running from their left eye to under their sweater.

"Let me go! Let me GO!" They finally noticed just who was holding them up. Their eyes grew wide and they bared their teeth. "It's you! Fight me you filthy sinner! I'll avenge Undyne if it's the last thing I do!"

"Calm down kid! I'm not gonna fight you." Sans' magic faltered as he heard a crash from the burger place. It wasn't much, but it was enough for the child to wriggle from the magic. They landed with a thump and jumped to their feet. Without any hesitation, they charged at Sans, nothing but fury in their eyes.

Sans scooped them back up again before they would trip on a bump in the carpeting. They floated a few inches above the ground, and was lowered down gently. They blinked once, twice, three times before turning to look at the skeleton.

"Be careful kid! You're going to get hurt if you don't watch out."

"Who are you?" Sans grinned wearily, really getting sick of that question.

"I'm Sans. Sans the Skeleton. It's a pleasure to meet you kid." He held a hand out in greeting, but realized the monster didn't have arms. He awkwardly let his hand drop to his side as the monster child gave him a sideways look.

"You're not Sans."

"I'm not… your Sans. It's a long story kid, but I'm not going to hurt you." The child narrowed their eyes with distrust. Sans held his hands up in a surrender gesture. "No really! I'm not the kind of guy to go around beating up kids."

"Why are you here?" The child's voice was still cold.

"I'm looking for my brother." In Sans' experience, it's best to tell as much as the truth as possible. "He's pretty tall, with spiky shoulders and a crack over his eye. He should be with a Robot?"

"I saw them…" Sans could have cried.

"Where? Where are they?" He took a step towards the monster child, who took three back in fear.

"Why should I tell you?" Sans stopped.

"You said you were going to avenge Undyne, didn't you? Why?"

"My parents were killed after you came to power. Undyne lied to the rest of the royal guard to protect me. I was going to help her in the rebellion but she was killed before we could join her cause. Now we have two reasons to keep going. Avenge Undyne and destroy Sans."

"We?" Sans knew he needed to find Papyrus, but this was just another piece in this confounding puzzle.

"Yeah. I have a small army behind me, and if I don't return to headquarters, they'll send someone to kill you guys."

"Wait kid… there's no reason to think about killing one another. What If I knew something that would change your world?" The child took a step forward, trying to be intimidating.

"What could you possibly know?"

"What if I told you where to find Undyne?" They narrowed their eyes and bared their fangs.

"Stop kidding around. She's been dusted."

"Tell me where my brother is and I'll tell you what I know." The monster kid paused, weighing their options. Sans could see it when they made up their mind when the emotions changed in their eyes, from cold anger to tentative belief.

"He took the robot and locked themselves in the burger place. I heard clicking and whirling. I don't know what he was doing though." He must have hooked Mettaton up to the battery and barricaded the door again.

"Oh thank god… they're safe…" Sans could literally feel a weight lifted from his chest as he turned to run to the burger stand. Just as he was about to take a step, something sharp caught his jacket and nicked his bottom rib.

Shouting some curses, he spun around and saw the child had a mouthful of his jacket and an angry look on their face. When they were positive Sans was going to stay, they spit out the fabric and took a step back.

"I told you what you want to know. Now, you tell me what I want to know." They had no mercy in their voice.

"Undyne is alive. She's at the rebellion base with a human." That was probably the last thing they expected to hear.

"What…?"

"You heard what I said. She's alive and still working on the rebellion. In fact, she'd probably be ecstatic to hear there are more for her cause. I'll take you to meet her, after I get my brother to safety." Sans waited for their response, itching to run to his brother.

"I'm going to go outside and report to my allies. If I come back and you're gone… you'll have an entire army out for your blood." Sans had to give it to them. For a monster that barely came up to his shoulders, they sure knew how to make a monster scared.

"I promise I'll still be here." Sans held his hand out again to seal his promise, and the monster child rubbed their head in his palm to seal it. They ran south, towards the door out, while Sans ran north, towards his brother.

"Papyrus let me in!" He banged on the door, only slightly desperate to make sure his brother was safe.

"Hold on Broth- Sans." Sans felt a twinge at the slip up, just another reminder that his wasn't this time line, this wasn't _his_ brother. A faint scuffling sound came from behind the door and it opened a fraction. When Papyrus was sure Sans was the only one, he opened it enough for the stouter skeleton to slip through.

Mettaton was leaning up against the counter, his face calmer now that he was getting some power.

"Sans take Mettaton first. I will stay behind to watch out for whomever was following us."

"About that bro… they're with the rebellion. The kid thought Undyne had really been dusted, and took up the cause themselves. Apparently they have a small army." Papyrus just blinked at Sans. The shorter skeleton gave him a reassuring smile.

"I'll take Mettaton back now, but you have to wait by the fountain for when the kid comes back. I have to take them to see Undyne, and they can't think I left them here." Just as Papyrus was about to protest, Mettaton began to stir.

"Oh… hello Sans. Thank you for… helping untangle me. I had… all but given up believing I would be saved." He opened his eyes – all four of them – and gave Sans a sharp smile. He finally had some color in his metal cheeks.

"No problem Mettaton. Anything for a friend…" He hesitated, not wanting to bring up anything touchy when the robot was in such a frail state.

"What is it Sans?"

"I was just wondering why you didn't…" Sans scratched the top of his skull in embarrassment.

"Why didn't I mistake you as the… Underlord?" Sans felt his face light up with a thick blush and Mettaton gave a kind chuckle. "You are very… different. Part of my programing lets me see… the souls of monsters. Your soul is a… wonderful shade of blue. The Underlord's soul is… a corrupt red."

"Ready to go somewhere safe Mettaton?" The robot closed his eyes and smiled again.

"Yes… please let us leave this place." Sans lifted Mettaton much like Papyrus had, letting him held his battery in his lap.

"Bro I'll be right back, just stay out by the fountain." Papyrus nodded in affirmation and headed to the door. He had one hand on knob when Sans stopped him again. "Thanks bro. You really are the best. I can always count on you."

Papyrus froze so violently he crushed the door knob in his hand. His shoulders tensed and he let out a choked cry before quickly exiting. Sans hefted Mettaton to a more comfortable position and flashed to Undyne's house.

Sans placed Mettaton with his back to the counters in the kitchen and put his battery next to him. When he phased back into the kitchen, the human and Undyne jumped to their feet and rushed to the skeleton. He held up his hand to silence them.

"I'll explain in a second, but I have to go get Pap." Sans flashed back to the hotel, right next to his brother. He fell to his knees, gasping for breath. He almost never used his powers, and never this much at once. His whole body felt cold. Sans felt Papyrus kneel next to him and place a hand on his shoulder.

The door opened and the monster child slipped back into the lobby. They saw Sans on the ground and let a flash of concern across their face before putting back on a mask of indifference. They walked up to Sans and cleared their throat.

Sans looked up and saw them, and tried to stand. He ended up needing his brother's help to straighten up. Sweat beaded his forehead in the exertion.

"Sans… maybe it would be best for me to carry you the long way back." Sans shook his head and doubled over as the room spun. He let the world settle before grabbing Papyrus' wrist. Despite the fact he was about to pass out, he didn't miss how Papyrus flinched and leaned away from his touch. He used his other arm to scoop the monster child up and flashed back to Undyne's for hopefully the last time for a long while.

Sans collapsed the second they made it to the kitchen, dropping the monster child on their butt. His whole body convulsed as the sweat poured from his head. Sans had never known pain like this. It wasn't like the time Frisk went on their Genocide run and killed him, or the pain he felt when he realized his brother was gone.

 _"…rest…Sans…"_ A voice filled his skull, causing tears to drip into the tiles of the kitchen floor. His body convulsed again, his spine arching painfully backwards.

"G…aster-"

 _"You… burned… out… you… rest… then… continue… save… time…line…"_

The voice faded as Sans' vision blacked out completely. One last thing got through Sans' blackness.

"BROTHER!"

* * *

 **I meant to update** ** _love yourself_** **but I felt like doing this instead… I also should have been doing my English work. I have two essays to read and peer review as well as make up a 6-7 minutes speech for Tuesday… oh well…**

 **Thank you everyone for the reviews, favorites and follows! I didn't know if anyone would like this headcannon for Underfell, but I honestly love the way this is coming out!**

 **If you have any suggestions, leave a review or message me! I'm always willing to incorporate a reader's ideas into my stories!**

 **Until next time**

 **~Starlight**


	4. Chapter 4

The first thing Sans heard when he came to was steady breathing. He was in a bed, that much he could tell by the softness under his fingers and the warmth over his legs. The second thing he noticed was he was underground. The mustiness and earthiness of the air gave it away. The third thing he noticed was something warm on his hand.

His vision began to clear and he saw Papyrus sleeping on the side of his bed, sitting on a chair with his head on the mattress and his hand wrapped around Sans'. There were faint blue streaks down his brother's face. With a start, Sans realized his brother had been crying. He was mumbling something in his sleep. Sans strained his hearing to understand what he was saying.

 _"I'm sorry brother… I know brother… stupid Papyrus…. Pathetic Papyrus… useless Papyrus…"_

He tried to sit up, tried to comfort Papyrus, but felt something painful hit him in the middle of his chest. He must have made some sort of noise because Papyrus woke up and immediately place a hand on Sans' back. The pain faded as quickly as it came, leaving Sans gasping for breath.

"Brother you need to lay back down. You burnt yourself out using your magic, and you've barely recovered." Sans refused, preferring to just rub his eyes to clear his fizzy vision a little more. It hadn't escaped his attention that Papyrus called him 'brother' without correcting himself.

"Where are we?"

"The underground tunnels under Undyne's house. She's been working on them since the start of the rebellion."

"What- how long as I out?" Papyrus looked to the side for a second.

"Almost three days…" Sans jerked upright and felt he room spin at the sudden movement.

"Three days? How's the kid? How's Mettaton? Did the rebellion make it? Is everyone safe?" He was afraid for everyone. Papyrus stared at him for a second before chuckling to himself a little. Sans gave him an incredulous look.

"Everyone is fine Sans. It's just… _you_ were the one unconscious for three days, yet you're asking about everyone else?" He chuckled again and placed a hand on Sans' head. "You're like nothing I've seen down here before."

Papyrus' soft smile made Sans tear up a little. It hurt him every time it became obvious his brother wasn't treated the way he should have been. Poor Papyrus should never be treated like he was nothing. Sans leaned over and grabbed Papyrus' wrist, despite the pain rippling through his chest cavity. His brother made a sound of protest but Sans ignored it, pulling the taller skeleton to his chest in a tight hug.

"You're not pathetic. You're amazing Papyrus. You're wonderful Papyrus. You're not useless. You're the Great Papyrus. You're not stupid. You're brilliant." Papyrus tried to struggle, but he really wasn't putting all of his strength into it.

"Sans… what are you-" Sans held him closer.

"You're amazing. You're the best. You're so reliable and smart and I'm so proud to have you as a brother. Thank you for looking out for me. I'm so proud of you." Papyrus stopped struggling and buried his head in Sans' jacket. He was still other than the faint shaking in his shoulders and the wetness soaking into Sans' shirt.

Sans reached out to wrap his arm around Pap's back when the pain in his chest came back full force. He dropped his arms with a strangled cry. His vision blurred and he heard Papyrus calling out to someone.

Metallic footprints came running towards them and Mettaton threw the door open. Papyrus pulled him over to Sans, who was curled in on himself. It was almost like his soul was being torn in two.

"Mettaton, is it still…?" Mettaton's second set of eyes glowed pink and Sans could almost feel his gaze going right through him.

"It's even worse than before…" Papyrus let out a low keen and Sans refused to be kept form the loop.

"W-what's going on?" He ground out from between clenched teeth.

"Sans… your soul is cracked, and it keeps getting…worse." Sans felt nothing. It was like all his senses had been turned off.

"Cracked?" By the look shared between Mettaton and Papyrus, he knew it was bad. "Will… will it heal?"

"We… we don't know. We don't have any healing foods left and no one here knows healing magic." Papyrus sounded pained. Sans gave a weak chuckle.

"Looks like I'm…" He cringed at another wave of pain. " _boned…"_

He smiled at his brother, trying to lighten the mood, and it worked to an extent. The corners of Papyrus' mouth quirked up an inch.

"Brother, you should rest. Undyne should be back from her scouting mission soon, and hopefully bring something to heal you with." Mettaton placed a hand on Papyrus' shoulder before whispering something to him and leaving. Just as the taller skeleton was about to follow, Sans caught the edge of his cape in his fingers.

"You called me brother…" Papyrus flinched a little.

"I-I didn't mean to-"

"Thank you…" a tear worked its way from his eye. Papyrus gave another soft smile.

"If anyone deserves to be called my brother… it's you." He leaned down and placed a kiss on Sans' forehead. "Now lay down and rest. I will return shortly with some food."

Sans smiled and plopped back down on the pillow. He didn't think he was that tired, but he fell asleep almost instantly.

* * *

Sans was in a dark room. If he could even call it a room. It seemed to go on forever, no end in sight. Something moved from his peripherals and he turned his head quickly…

But there was nothing there.

"Sans…." A voice echoed from everywhere and nowhere. Sans spun around, trying to pinpoint where the voice was coming from.

"W-who's there?"

"Sans… the… lucky… one…"

"What do you mean? Who are you?"

"Powers… too… dangerous…" Sans spun around again, his eyes finding nothing but darkness.

"But I managed to control them."

"He… did… not…" A flash of red caught his attention. Sans slowly turned his head and found himself face to face with a large mirror. It was easily two feet taller than him, and twice as wide. The edges had golden designs and the glass was spotless, almost like there was nothing there at all.

Sans stared at his reflection, not quite understanding what he was seeing. It was just him…

He took a closer look and let out a light gasp.

It was him alright… but not him. His reflection had sharp fangs, far sharper than his own canines. The reflection smirked at him, but Sans himself didn't move an inch. The reflection's left eye burned to life, the scarlet magic flaring brilliantly.

Sans fell back in shock, the reflection chuckling darkly. He lifted a shaking hand and touched the glass, the reflection's hand doing the same. Just as his fingers touched the glass, the double lunged forward and grabbed his wrist.

"Look… closer…" The same everywhere but nowhere voice called to him again. Despite every inch of his body screaming at him to run away, Sans looked closer.

Although this other Sans had a crazed look in his magic eye, his normal eye seemed… sad.

Sans understood.

"I managed to control my magic…" The reflection's mouth followed Sans' movements.

"But mine controlled me…" the real Sans hadn't moved, but he watched as the reflection formed the words. As the last syllable sounded, the mirror shattered, Sans' wrist suddenly free. The broken glass fell slowly, and Sans found himself falling as well.

A pair of arms caught him in his descent, but just for a moment. A hand reached into his chest and cupped his soul gently. Sans cried out at the intrusion, but a familiar cold sensation ran over the little heart before the arms let him continue his fall.

"Save… him…"

* * *

Sans woke with a start, his breathing fast and his magic thrumming though his body almost painfully. He gasped for breath, waiting for the painful thrumming to stop so the pain in his soul could take over, but there was none.

He blinked and twisted his torso to the left and right. No pain. He grinned and laughed to himself. He threw the blankets off and jumped to his feet. The room still spun a little, but that's just because he had been bed ridden for three days.

He let go of the bed, which he grabbed to steady himself, and saw his blue jacket slung over the chair Papyrus had been sitting in. Shrugging it on, he noted a slight twinge in his ribs. Uncomfortable but not painful. A reminder of another run, long, long ago.

Sans opened his door carefully and gasped at amazement at the sight before him. He was expecting simple dirt hallways, but then again Undyne wasn't one to do things half way. The hallway overlooked an open area. Moving over to the wall, Sans saw there were three levels of hallways, all with doors facing this open area. The walls had been covered in some mixture that was rock solid when Sans tapped it with his knuckles.

Looking down, he saw figures of all shapes and sizes sparring in the open dirt. Undyne was standing on a dirt mound, overseeing the action. There were thirty monsters at least, many of them smaller in size.

The figure in the middle of the field caught his eye. Frisk was sparring with the armless monster child, both holding their own fairly well against the other. Sans watched in fascination as the monster made up for their lack of arms by using kick attacks, the kid made up for their size by ducking and dodging like a pro.

Smiling softly, Sans made his was down the carved out stair and to where Undyne was overseeing. She didn't seem too surprised at his sudden appearance, but hopped off her pile to talk to him.

"Pretty sweet set up you got here Undyne. How long did it take you?" Undyne shrugged nonchalantly and gazed around.

"A long time. Thankfully I knew some mining magic from the last head of the royal guard, so I didn't have to rely on all muscle to get the job done." Sans hummed in response, his respect for the fish woman growing several notches.

"Any idea where my bro is?" She lifted her spear and pointed up and over a little.

"Third hallway, fifth room from the staircase. That's the meeting hall. He should be in there with Mettaton."

"Thanks Undyne." Just as he was about to leave, Sans stopped. "Oh and… make sure the kid doesn't work too hard. They're too nice to have their spirit broken in training."

Undyne flinched, and Sans grimaced. He didn't know what she was thinking of, but he was brought back to him own time in the guard. He waved a hand lazily in the air and walked off. As soon as he was out of sight he made to teleport, but remembered what happened last time.

Grumbling under his breath, he climbed three flights of stairs. If he had lungs, they would be burning. He knocked on the door once before throwing the doors open. Part of him hoped to catch Pap and Mettaton in a compromising situation, like he did back in his timeline.

That small part was partially rewarded, for the two moved away from each other suddenly. They had been seated at the long table, head in close together, murmuring about something. Sans noticed with glee that both had a faint blush on their cheeks.

"Sorry to interrupt the love fest, but I have something interesting to tell you guys."

"L-love fest? Sans I really… don't know what you're talking about." Mettaton's speech pattern continued to grow smoother.

"Brother? What are you doing out of bed?" Sans waltzed over to where the other two were still seated and sat on the table.

"That's kind of what I wanted to talk to you about." Mettaton, could you take another look at my soul?" The robot nodded once and opened his second pair of eyes. They stared though Sans for a moment before widening with shock.

"You're all… better?" Papyrus made a sound of surprise, but that's not what Sans wanted to know.

"I guess so, but can you see if there's anything different?" That cold sensation had to mean something. Mettaton looked again, this time with both sets of eyes, probably to help him concentrate more.

"It's not better, but it's not… cracked anymore. The cracks have been sealed by… something dark. Almost like black… glue or paint." Sans had a sudden flashback.

He was watching the timelines. Black paint dripping into the colors. A cold sensation on his forehead. That voice… That voice! His eyes grew wide as he finally made the connections in his head. The shadow man… Gaster. He did something to the timeline. He somehow warned Sans about the monster child back at the hotel. He spoke to Sans in his dream.

Sans groaned and placed his head in his hands. Papyrus and Mettaton leaned in closer to see what the matter was. Without lifting his head, he summed it up as simply as he could.

"Guys… this whole thing just got a thousand times more complicated."

* * *

 **So next chapter should have more action. This was just to set some background information and set up for the plot ark at the end. I'm thinking confronting Alphys, or maybe more brother bonding. In the game each character had something you had to fix before you could spare them, and I'm thinking of having different things need to be met to save these guys.**

 **I'll have a whole explanation for how I got the Underfell personalities near the end, like why I decided to have Sans be the bad guy, or why Toriel tried to attack Frisk at the beginning. Believe it or not I actually have solid background for all these characters.**

 **Also, if anyone has any questions, is confused about anything, or has suggestions, leave a message or a review! I'm always eager to hear your thoughts about the chapters!**

 **Until next time**

 **~Starlight**


	5. Chapter 5

Sans looked down the table, looking at everyone gathered at the table. After his revelation with Papyrus and Mettaton, he called for a meeting. It was the usual gang, Papyrus and Mettaton, Undyne and the Monster child, Frisk and Flowey.

"So why the meeting Sans?" Undyne was the first to speak after everyone was gathered around and seated.

"I think I know what we have to do next, but it's almost definitely a suicide mission." The gathered monsters mumbled fearfully.

"Brother what is your plan?" Sans gave a weak smile and cleared his throat nervously.

"I think I know who messed with the timeline, and there's only one person I can think of that might know anything about him." Undyne grinned and stood, planting a foot on the table.

"Then what are we waiting for? Let's go get them and force them to tell us that they know!" Sans flinched at her enthusiasm.

"A-about that…" Undyne seemed to deflate a little at his tone. "That monster is… Dr. Alphys."

Instantly the room erupted. Undyne sat with a dead look on her face, but Papyrus stood, yelling at Sans. Frisk and the monster child began babbling in fear and nervousness. Mettaton was trying to get to Papyrus, and ended up speaking over most of the noise.

"Brother what the hell do you think you are implying? Alphys is almost as bad as-"

"Me, I know." Sans didn't let the volume of Papyrus' voice get to him. "I know she did some awful things… which is why I'm going alone."

The room was wrapped in silence for a heartbeat. Then all hell broke loose. Papyrus tried to lunge for Sans, Mettaton using all four arms to hold him back. Frisk had jumped up and ran towards Sans, gently punching his chest. Undyne jumped onto the table and was threatening to beat some sense into Sans.

The shorter skeleton was starting to get a headache but knew he wouldn't be able to talk over everyone. With a glow of the eye and a flick of the wrist, everyone found themselves back in their chairs, unable to stand up.

"Alright can I finish? Anyway, I'll be going alone because hopefully she'll think I'm the other Sans long enough for me to trap her, and if she saw you" He pointed at Undyne, "Or you." He pointed at Mettaton, "She would instantly know something was up."

"Sans you can't seriously think-"

"Besides… I can't risk any of you." Papyrus made a noise but Sans knew if he looked over he would lose what little cool he had.

"You seem pretty calm about this." Mettaton sounded as calm as Sans wished he felt.

"As of now, this is the only option." Sans let his magic up, and everyone shuffled in their chairs. Frisk was the only one who stood. They ran right as Sans and wrapped their arms around his waist.

"Don't want Sansy to go…" Sans ruffled the kid's hair and gave them a reassuring smile.

"Don't worry about me Kiddo. I'm strong." Mettaton whispered something to Papyrus.

"Come along Human, Undyne, Flower monster and Child monster. I do believe it is time to head to the mess hall. Please follow me." Papyrus led the parade of allies out of the room, leaving Mettaton and Sans alone.

"Look Mettaton. I'm not going to change my mind." Mettaton held a hand up.

"I'm not going to try to make you change your mind. I'm just going to…. Prepare you for what you might face." He stood and held out all four arms. "Do you know the full story about what happened to me?"

"N-no. Papyrus gave us a brief overview but…" Mettaton gave a sad smile and gestured for the skeleton to sit.

"The Underlord gave me very strict guidelines to follow… but I refused to follow them. I wanted to perform my way, not his way. I thought I was being… sneaky, but he found out. I was performing for a large crowd, the last crowd I performed for. His… royal guard came up to me after the show and electrocuted me, frying my circuits.

"I woke up on a cold lab table. My wrists and ankles were strapped down, as was my head. I could not… see anything other than the light directly above me. I heard her from the other side of the room… muttering to herself and chuckling.

"I tried calling out to her, but my vocal box was not working. She saw I was… awake and came over. She changed since building my body. She looked crazed, crazed and broken. She said something to me, but I couldn't… understand anything. She jabbed something into my chest and it jumped my circuits. I could hear rumbling and whirling from all around me.

"She stood over me, but someone else started talking. The whole table moved and I saw him. The Underlord stood before me, grinning sadistically. He held up a ripped painting to show me. It showed two masks of sorts, one happy and… the other sad.

" _If you want to perform so badly,_ he said to me, _so I decided to let you be the ultimate performer._ Alphys moved closer and started welding, pulling me apart piece by piece. They never turned me off, so I was awake for it all.

"To this day I have no clue how long she worked on me, but I know it must have been weeks. She had made me into an abomination, two within one. They found irony in turning me into two robots in one body. The top eyes and arms were to represent the grinning mask, while the bottom arms and eyes were the grimacing mask.

"Somehow, they split my soul in half. They removed it from my body, trapping my ghost inside the metal prison… I could not escape. They put one half… towards the first set. The second half to the second set. Every couple of days Alphys would… pull me back to rearrange my parts again. It was excruciating…. She wouldn't let me sleep at all so I was constantly awake and … experiencing everything…

"Eventually, I managed to subdue the other set, but not before… tangling myself up in the process. The Underlord must have… gotten bored with me. For the first time in months I was switched off… and when my automatic restart booted me back up, I was on the stage, in the dark.

"I tried… radioing for Papyrus, but they removed my radio. There was nothing for me to do… but wait until I expired completely. I had maybe a month or so left when… you found me. I am in your debt for saving me, which is why I am telling you this.

"Alphys has no empathy anymore. She willingly ripped me apart time and time again without remorse. You must be… careful Sans. If anything were to happen to you, Papyrus would be destroyed. He never had… someone to care for him before."

Sans sat in silence, his eyes wide and his jaw hanging low. Out of everything that he could have expected, this was not it. A chill went down his spine. He never knew just how sadistic this other version of himself was.

"Mettaton…" The robot gave him a small smile.

"Do not pity me, Sans the Skeleton. I did not tell you this… for pity."

"Mettaton do you love Papyrus?" That was the last thing the robot was expecting to be asked. His arms moved around a little like snakes before stilling. Both sets of eyes were wide and a faint blush on his cheeks.

"S-sans I do not t-think that is relevant…"

"To me it is. Do you love my brother?" Mettaton looked at the ground sheepishly.

"Yes… yes I do love Papyrus." Sans felt a weight lifted from his chest. He moved to stand in front of Mettaton and took one of his hands.

"Please… if anything happens to me, please take care of him. He needs someone to show him love." Sans gave a small smile and went to leave. Mettaton caught his sleeve and forced the skeleton to look at him.

"Sans, what do you mean? Are you expecting to…?"

"I honestly don't know what to expect. I might be dusted in an instant, I might fix everything and won't come back here… Please just take care of him." It looked like Mettaton wanted to say more, but Sans turned and left, gently pushing the doors open.

He stopped dead, seeing Papyrus standing on the other side, arm outstretched as if to knock. His eyes were wide and his jaw slightly open in shock. Sans could have sworn his brother's skull was a shade or two whiter than usual. How much did his brother hear?

"B-brother…" This was the last thing Sans wanted to face right now. He was planning on leaving in the night, when Papyrus couldn't be there to see him go. Sans sighed and closed his eyes. Reaching out, he brought his brother into a hug. It was a little awkward, Papyrus being a good foot taller than Sans, but neither complained.

"Pap… remember that you're a good kid. You're amazing and loved. Please don't think you're anything else, even if something happens to me."  
"But Sans-"

"Promise me Bro!" Papyrus sagged a little, defeated.

"I…I promise brother." Sans dry sobbed once into his brother's chest before pulling himself together. He pulled away and straightened his jacket.

"Hey bro, do me another solid?" Papyrus gave him a sad look, not responding. "Don't let the kid know what happens to me. They shouldn't have to deal with that."

The taller skeleton just nods slowly and places a gloved hand on Sans' shoulder

"I wish you would allow me to accompany you." Sans chuckled and walked out the door. He paused for a second and tossed a last comment over his shoulder.

"And tear you away from your lover boy? I'm not that heartless." He winked and used his magic close the door behind him. Papyrus looked at the closed door, not moving. Mettaton went over to the skeleton and wrapped his arms around his waist.

"Are you okay hun?"

"I finally got the brother I always wanted, and now he's walking right out of my life. I'm just _letting him leave me_ … and there's nothing I can do to make him stay." Tears welled up in his eyes, the dark blue dripping from both eyes, dripping quickly from his good eye, squeezing through the crack in his bad one.

"Oh darling, he's doing this to save you." Papyrus broke away from Mettaton and stalked over to the table. He placed both hands on the surface and rested his weight on them, hanging his head and trembling. "I've never seen you this worked up before…"

"I always loved my brother… even before he cracked my skull. He was never _bad._ He just lost control sometimes. The real Sans in still in there, I know it…"

"Is that why you stay around him, even though Undyne tries to convince you to leave?" Papyrus' hands clenched into fists on top of the table.

"I know there's still good left in him… Oh Mettaton I feel like I have lost two brothers…" A sob wracks Papyrus' body and Mettaton wraps his arms around him again.

"Don't worry dear. That Sans is quite resourceful. He'll be back by morning, no doubt about it." The robot tried to keep the doubt from his voice.

"I know you are only lying to me in order to bring me comfort, and I appreciate it. Thank you Mettaton." Papyrus sighed and straightened.

"Anything for you darling." Mettaton placed a soft kiss to the side of Papyrus' skull. The skeleton turned into the robot's embrace and cried himself dry for the first time since his brother cracked his skull all those years ago.

* * *

 **So another shorted chapter, but I thought this was a good place to end off. Next chapter will pick up with Sans at the Lab!**

 **Do you like how I'm writing the Underfell characters? I tried to make it all link, and I can explain a little bit of it now. I'll explain the rest as the story continues.**

 **So Underfell Sans has the same powers as regular Sans, but was unable to contain it. The magic took over and caused him to lash out at his brother, causing Papyrus to become bitter and grow up scared of his Sans. Undyne is more subdued because of how Alphys treated her when she tried to fake her death. Mettaton is also more subdued because of his past trauma. Flowey is nice because… well we'll get to that in the next soliloquy, same with Alphys. I have reasons, but I don't want to spoil anything.**

 **If you're confused about anything, shoot me a message and I'll try to clear things up the best I can! I'll also be explaining it more as the chapters progress. I really am enjoying how all of this is turning out!  
Thank you for all the love you guys have given me! I'm beyond overjoyed that you guys actually like my writing! **

**If anyone has any ideas or suggestions, don't hesitate to tell me. My main goal is to improve myself as a writer, and I can only do that though practice and feedback. I have the first part going strong, but I need your help to get the second part rolling!**

 **Until next time!**

 **~Starlight**


	6. Chapter 6

Sans stared up at the Lab, a dread dripping down his spine. He tried to recall the reflection from his dream and recreate the smirk on the other him. The sadistic smile felt wrong on his face, but he only had to keep it for a little while.

He knocked on the door, curling his grin into something even more feral. A voice called through the lab and footsteps make their way to the door. Expecting Alphys, Sans held his sneer. It was not Alphys that open the door though.

In his shock, Sans dropped the sneer. Standing before him was a robot, similar to Mettaton's build before the modifications, except with a blue and silver color scheme. His hair was silver rather than Mettaton's black, and his eyes were scared rather than prideful. The robot took one look at Sans and began shaking.

Sans was expecting to enter into a battle, but saw the robot in front of him was in no state to fight.

"Y-your Majesty! I w-was not a-aware you would be s-stopping by!" He squeaked, almost in tears. Sans felt the urge to wrap the robot in a hug, but remembered his mission.

"Where's Alphys?" He tried making his voice deeper, and it must have been close because the robot let out a squeak and a spark flew from his head.

"In her l-lab, sir." Sans took another look at the robot as he walked through the door frame. He was shorter than Mettaton, but had the same basic structure. One thing he noticed was the lack of a heart on the abdomen of the body. The feeling of dread returned as he made connections in his head. He stopped and turned to the robot.

"Who are you again?" Sans knew he was treading on thin ice, but the nagging in the back of his head wouldn't let him walk past without asking.

"Napstablook, sir. We've met o-once before." Sans felt a cold sensation and knew it was Gaster trying to tell him something. He took a deep breath and fit that awful sneer back on his face.

"Come with me, robot." He walked back out the door and waited for Napstablook to follow. As soon as they were clear of the lab's immediate cameras, Sans grabbed the robot's wrist and teleported away.

They landed in a clearing back in Snowdin, a clearing that Sans hoped was still unknown to most monsters. He knew he blew his cover, but he couldn't leave Napstablook in that hellhole. The robot in question had backed away in fear.

"W-who are you?"

"My name is Sans, but I'm not the Sans you know. I'm going to try to get you out of that body and-"

"No!" Napstablook cried out, starling Sans.

"No? Don't you want to…?"

"N-no. I went to Alphys to get this body. I just didn't expect her to…" He flinched.

"What did she do to you?" Sans took a step forward and Napstablook sighed, wrapping his metal arms around his torso in an attempt to comfort himself.

"She… she trapped me. She put in a sensor that would shock me if I ever walked over the property line of the lab. She made me her servant… but I guess I deserved it. I didn't get there in time to save my cousin, and I wasn't strong enough to escape myself…"

"Since I teleported, the sensor didn't shock you, right?" Sans wanted to make sure he was alright. Napstablook nodded and smiled shakily.

"T-thank you for rescuing me. I thought I would be her test dummy until I was dusted…"

Despite the relief rushing through Sans, he knew he compromised the mission. He clenched his hands and opened them over and over.

"Listen to me carefully. Go to the fish shaped house. Knock twice loudly, twice quietly and one more time loudly. When someone opens the door ask for Papyrus. Tell him I sent you. You'll be safe with them." Sans was startled by the sudden appearance of tears in the robot's icy blue eyes.

"T-thank you… thank you so much."

"Don't mention it. Literally. Don't mention I saved you to anyone but Pap because it could put you in danger again." Sans pointed the direction Napstablook should start in and teleported back to the lab. He heard muffled alarms and wished he had given Napstablook a message for him brother, but it was too late to turn around now.

He took a step forward and opened the door. Steeling his nerves, he walked into the blackness. Something hit him upside the head, knocking him unconscious.

* * *

Napstablook stood nervously in front of the door. He tried to remember what the knock was, but in his nervousness, he managed to mix it all up.

"Was it two soft, a loud and a soft? No… it was two loud and a soft and… another soft? Oh dear I knew I would mess this up. I mess everything up." He was muttering to himself, his fist hovering three inches from the door.

He knocked twice loudly. He remembered that much. Then it was… two soft? He knocked hesitantly twice. He heard rustling from behind the door and felt his nerves shoot through the roof of the cave. He began muttering to himself again, frantically trying to recall the last thing. His mind was a fuzzy mess. His circuits jumped from his nerves and his fist smacked the door loudly.

"Oh dear… oh dear what if that was wrong? Oh no they won't let me in… Alphys will find me again! Oh no, oh no, oh no…"

But he was worrying for nothing, because the door opened to reveal a small monster with huge ears and a large scarf wrapped around her neck.

"That was the right code. What is your business here?"

"I-I'm here to see, um… P-papyrus?" Napstablook's voice trembled. The monster eyed him suspiciously for a moment before ushering him in the house. The house itself was a single room, with a big kitchen, a piano and a door going to another room. She led Napstablook over to the piano and used her magic to pull it to the side. Under the rug that was under the piano was a trap door. Under the trap door was a set of stairs, cares from the rock.

Napstablook followed the monster down the stairs, only squeaking a little when the trapdoor swung shut behind them. The only sounds were the piano scraping back into place, and the only lighting came from small balls of magic floating along the top of the hallway.

They came to a door at the end of the stairs. The monster pushed it open and Napstablook felt his jaw drop. It was like a catacomb, he thought. Three levels of rooms circled a large open area at the bottom of the room. There were monsters of all shapes and sized scurrying and flying and jumping about, some sparring on the field, some carrying boxes, others just moving from one room to another. He had never seem anything like this.

Napstablook was led to a door a few down from the staircase. The little monster knocked twice and a voice from inside called for them to enter. She opened the door and gestured for Napstablook to enter first. She followed in after, closing the door almost all the way.

"Someone here to see you Papyrus." She bowed a little and slipped through the crack left in the door. The click of the door seemed to echo though the large room. Napstablook gulped and wanted to turn tail and run right there.

"H-hello-"

"Who are you?" Papyrus wasted no time with strangers. "You obviously knew the code. Who told you?"

"Um…" Napstablook remembered what Sans had told him, but Papyrus was just so intimidating. "I um… the p-person who told me… um… My name is N-nap-"

"B-blooky?" Napstablook had noticed a second figure in the room with Papyrus. This second figure was tall, with shaped hair and four arms. They stepped into the magic fire light and Napstablook felt tears in his eyes.

"M-mettaton?" The taller robot threw himself at his cousin, almost knocking the smaller off his feet. Mettaton began sobbing into Napstablook's shoulder, wrapping all four arms around him.

"Oh Blooky I'm so sorry! I never should have left you… I should have looked for you. I'm so sorry… I've failed you!" Papyrus stood awkwardly by the table as Mettaton apologized again and again.

"N-no, I'm sorry. I wasn't strong enough to rescue you…" Napstablook wiped the tears from Mettaton's face.

"What do you mean Blooky dear?"

"I um… I went to Alphys to get this body so I could save you. But by the time she put me in it, you were gone from the lab… and I was trapped there."

"Erm, Napstablook, was it?" Papyrus interjected. He could see Mettaton about to explode and wanted to avoid that. Poor Napstablook would be getting an earful soon anyway. "Yes, well… if you were at Alphys lab, did you happen to see a short skeleton? With a blue jacket?" He almost didn't want to get his hope up, but he needed to know.

Napstablook removed himself from his cousin's arms and went over to the tall skeleton. He placed a metal hand on his bone arm.

"Yes. He said his name was Sans…"

"Y-you! That means he's safe?" Papyrus saw Napstablook's face fall.

"He was muttering under his breath. He said the mission was compromised?"

"He was going to trap Alphys by pretending to be his other self…" Papyrus was talking more to himself, his words soft.

"Oh dear… oh dear, oh dear."

"What's the matter Blooky?" Mettaton didn't like the tone in Napstablook's voice.

"Alphys must have been alerted when he helped me escape… She would have been waiting for him." Papyrus froze. Not again…

"Mettaton, can you take Napstablook to find an empty room. The one next to ours should be vacant. It was meant to be for... He's probably very tired from today. He deserves someplace safe to rest."

"But darling-"

"Trust me on this Mettaton." Papyrus sat at the head of the table, his back to the door and the two robots. He heard some whisperings and a door opening. Then the door closed and he was left in silence.

He had been toying with the idea of going after his brother, but now…

Now his brother needed him more than ever. But how was he going to make it out of the tunnels without anyone spotting him or trying to follow him? Sighing, Papyrus wracked his skull for an idea, something… _anything_.

Suddenly, something popped into his mind. He stood and stared at the spot at the farthest end of the table. Concentrating, he envisioned himself in that spot. He felt his magic swirling around in him, almost bubbling up. He remembered the trouble his Sans had controlling this power, and for a brief moment was afraid of it overpowering him also.

Papyrus shook the thought from his head and forced the magic to obey him. He summoned the swirling magic and focused on the spot just next to the chair. Suddenly, he felt as though he had been rocketed though the air.

Just as suddenly, he was standing upright again, except now he was on the opposite end of the long table. Papyrus let a grim grin of satisfaction light up his face. He did it again, and again for hours until he was confident in his ability. He was unsure still if he would be able to teleport all the way to Hotlands, but he had to.

Papyrus adjusted his cape and left the conference room. He went to his own room. Opening the door, he found a piece of paper and jotted down a quick note in his scrawling handwriting.

 _Dearest Mettaton, please know I'm not doing this to spite you. Farthest from it actually. I must follow Sans and fix this timeline in order to give you the life you deserve. Please do not hate me for this. I do not think I would be able to live with you hating me. It's just so unfair… I just got you back and now I may never see you again. I love you dearly Mettaton. Take care of everyone for me. You were always so much better with others… With all the love a skeleton can hold, Papyrus._

Dark blue spotted the page in certain places, but Papyrus just blotted the tears away. He folded the note and looked around. Spotting his sword, he clipped it to his belt and left, not needing anything else. He went one door over, to the room Sans stayed in when he passed out.

His fist clenched, remembering how he felt a few days ago. He was ecstatic that his brother would be one room away from him, but now… Papyrus pushed the door open gently and saw Mettaton and Napstablook on the bed, hands entwined. Napstablook was quietly snoring, a faint smile on his face. Mettaton was breathing heavily, a slight line of drool coming from his open mouth.

Papyrus smiled fondly at the robot and felt his soul contract. He almost doubled over in pain, and he remembered the cracks in Sans' soul. With cold dread running down his spine, Papyrus went over to Mettaton and placed the note in his open hand. His fingers automatically clenched around and he snorted in his sleep. Papyrus leaned down and placed a kiss on Mettaton's forehead, almost certain this would be the last time he would see the pink robot.

"I l-love you Mettaton." He whispered, his voice cracking painfully. Mettaton stirred slightly and rolled over. He smiled and through sleep bleared eyes saw Papyrus.

"Love you too darling." He slurred before turning back over and falling back to sleep. Papyrus straightened and took one last look at Mettaton's still form before turning on his heel and going back to his own room. He wrote anther note, this time to Undyne. It was maybe three sentences long. It simply told her that he left to help Sans, and to make sure Mettaton stays safe.

He left it on his pillow, knowing it would be found sooner rather than later. He sat on the edge of his bed and let his mind clear. He focused on the swirling magic within him and pictured the labs. He imagined the heat and the beeping that always came from that damned building.

With a lurch, Papyrus' magic catapulted him through space. He landed in front of the labs, stumbling a little as his feet hit solid ground. He immediately doubled over and retched, the toll on his magic too much. He heard a cry from inside the lab, and felt ice strike his soul.

He would know that cry anywhere.

"Brother!"

* * *

Sans found himself strapped down, and faintly recalled how Mettaton explained being held down. A small part of him appreciated the irony, but the bigger part was trying to wake up entirely. With his 1 hp, he thought that hit would have dusted him for sure, but he seemed fine other than the faint throbbing in his skull. He was reminded of the onetime Grillby challenged him to a drinking contest… He learned quickly not to accept a challenge to drink from a fire being.

Sans heard shuffling from his left side. He tried turning his head, but his forehead had a strap across it, keeping him looking straight up. The light above him would have blinded him, if he had actual eyeballs to be blinded.

The table started vibrating as what sounded like gears began turning. The table lifted and Sans found himself looking in a mirror, like in his dream. Except this wasn't a dream, and that wasn't a mirror. The other Sans chuckled at the scared look on his face.

"Aw, you look confused. What did you expect? Did you really think I wouldn't find out about another version of myself in the Underground? You'd be surprised how many spies I have throughout these shitty caves."

Sans didn't know what to say, so he did the next best thing. He spit right in the other Sans' face. With an infuriatingly calm face, the other Sans wiped the blue tinted spit from his skull and looked at it, the blue standing out against his black gloves.

"Blue, huh? You really are too good for this world."

"Why did you hurt Papyrus?" Sans managed to growl out. The other Sans raised his brow bones, almost surprised at the question.

"That useless bag of bones?" Sans felt his soul boiling in rage. "He got what he deserved."

"How dare you! How _fucking_ dare you treat Papyrus like that!" Sans pulled against his restraints as he screamed at himself. Alphys squeaked from the other side of him as the seams of the restraints began to pull apart from the strain.

"Now, why would you be getting all worked up over my brother?" The other Sans seemed to be getting a kick out of teasing Sans.

"You have no right to call him your brother! I've heard what you called him, and I'd bet any amount that you're the one that cracked his skull."

"So what if I did? What are you going to do about it?" The other Sans' eye glowed blood red. Sans summoned his magic, only to find it had been blocked somehow. He frantically reached for his magic, but there was nothing there for him to grab. The other Sans laughed darkly. "Oh, I see you've noticed the magic blocking binding we used. My dear, dear Doctor Alphys here invented them herself. I'm oh so proud of what she has accomplished."

A light whimper came from Sans' left and he felt a cold sensation wash through him. He could tell something was wrong, but he wouldn't be able to help anyone being strapped down. He struggles against the bindings, hoping to pull the seams enough for them to snap, but it was useless. Whatever the straps were made out of, they were a hell of a lot stronger than him.

The other Sans walked over to where Sans assumed Alphys was and picked something up. By the sound of it, it was something metal. The other Sans walked into view again, this time holding what looked like a double pronged fork. It was larger than a dinner fork, almost the size of his hand, and the handle had blinking lights on it. The other Sans came closer to the table and with his free hand, ripped the front of Sans' jacket off, his claws catching on Sans' ribs.

"Now, tell me a story, will ya Sansy? How did someone like you end up in my world, huh?" The other Sans grinned sadistically as the silence that followed his question. Hitting a button on the handle of the device, he place the prongs delicately on the bottom left rib of Sans' torso.

Immediate pain flooded Sans. His back arched as much as the straps would allow him and he couldn't stop the cry that ripped it's was from his mouth.

"Now, now, now. No need to be so unreasonable. Just tell me what I want to know… Alright, how about this one? Where is Undyne's rebellion?" Silence. Another button push and another placement on the rib, this time one above the last.

Sans had never felt such pain before. He writhed on the table, pulling against his restraints with as much force as possible. This scream went past inhuman. Sans wished he could just be killed. Anything would be better than this.

"Alphys, the little dear, invented this especially for you. It's designed to force electricity laced magic through your bones and eat away at the magic lingering in you. Each time I press this nifty little button here, the power goes up and it eats away more and more of your magic. Eventually, it'll eat up all your magic and attack your soul."

"You sick bastard." Sans ground out through the pain.

"I knew you'd understand." The other Sans gave a sickly sweet smile and pressed the button a third time threateningly. Suddenly a crash sounded through the lab. The other Sans fell back with fear in his eyes before barking some orders at Alphys.

Out of the corner of his eye, Sans saw the little yellow monster scurry out of the lab and into the main section of the building. The two Sans stood in silence, listening to the crashing and banging from above them.

An earth shaking explosion sent Alphys back down the stairs, crashing into the hard ground and denting the rock. As the dust cleared, Sans saw a tall figure walking down the steps.

"B-bro?" Sans couldn't believe his eyes. Papyrus was standing there, a dark blue bone clenched painfully in one fist. His left eyes was glowing a dangerous dark blue and his grin was almost as sadistic as the other Sans.

"You took Mettaton. You took Napstablook. You killed so many… and now you've taken my brother from me. Now, you are going to pay."

"I took your brother? Are you as dumb as you are useless? I'm your brother, not this sniveling mess." The other Sans pointed his device at Sans, causing the skeleton to shrink in fear. Papyrus saw Sans' reaction and cried out in rage.

He charged at the Other Sans, his dark blue magic sparking and flaring up. The Other Sans grinned at his brother and shoved the device right into the middle of Papyrus' ribcage. The initial impact was silent, but the howls of agony coming from his brother's mouth made Sans see red. Papyrus collapsed into a motionless heap.

"No… no… not again… no, no, NO, NO NONONONO!" Sans heard nothing but the roaring in his skull. He saw nothing but the red covering his vision. He felt nothing but the throbbing rage coursing through his body.

His magic swirled to the surface, despite the magic restricting straps holding him down. The straps burst, the enchanted fabric shredding and fluttering to the ground. Sans slid to the floor, his feet hitting the ground with a muffled thump. The Other Sans still had his back to the lab table, and he didn't notice the crackling magic from behind him.

The Other Sans was kneeling at Papyrus' side, muttering something and holding a gloved hand. If Sans had been in his right mind he would have noticed the shaking in the other's shoulders, or listened to the trembling whispers of _oh god no not again_ , but he noticed none of this.

Sans' magic flared to life, engulfing his whole body in flickering fire. Alphys cried out, hiding behind the lab table and watching from around the corner. The Other Sans felt himself lifted away from his brother and dangling in the air on front of Sans. The Other Sans shuddered at the feral look n his double's eye. He had never been this afraid of another monster before, expect for himself when his magic went out of control. Ironic how it was himself scaring him now too.

Sans' mouth curled up into a grin and he let out a dark chuckle. He brought the Other Sans close to his face and used his free hand to grasp the other's collar.

"You're going to have one hell of a _bad time."_

* * *

 **Oh wow alright definitely not a short chapter.**

 **The whole thing was just supposed to be the confrontation between the Sanses, but someone asked where Blooky was, and my heart reached out. Napstablook is one of the characters I connect most with, and I almost forgot about him!**

 **Looking ahead, I'm thinking one or two more chapters and a conclusion. I'd like to say thanks to everyone who's stuck with this and given it so much love!**

 **Until next time!**

 **~Starlight**


	7. Chapter 7

Mettaton was beyond hysterical. The other monsters were honestly worried for his health at this point. He had woken up half an hour ago, smiling as he recalled the dream he had of Papyrus. He stretched, thinking of the tall skeleton. He heard a crinkle of paper coming from his hand and opened one eye.

In his hand was a piece of paper, and he instantly recognized the handwriting. Expecting some sort of love note, something they would often exchange before everything went downhill, he read the first line with a smile, but soon realized it was nothing to smile about.

By the time he got to the end, Mettaton was sobbing. Napstablook was woken by the sounds of his cousin's cries. Groggily, Napstablook rubbed his eyes and tried to ask what was wrong.

"H-he's GONE!" The only thing running through his head was _oh god he's gone. Papyrus is gone. He left me. He's going to die and I'll never see him again…_

"W-wait maybe he isn't really gone?" Napstablook had no idea what to do. He was usually the one crying, and Mettaton was the one comforting him. "M-maybe we should do talk to Miss Undyne?"

Mettaton jumped out of the bed and ran over to the room next door. Before opening the door, he prayed to see Papyrus in their bed. Of course, the bed was made and the room was cold. On the pillow was another note, this one addressed to Undyne.

With shaking hands, Mettaton read that one too. Now it was real… his Papyrus was going to die and there was nothing he could do about it. He fell to his knees, staring blankly at the note, not noticing the pink tears falling from his eyes.

Hands touched his shoulders, but he didn't care. A voice called to him, but he didn't hear them. He had lost his entire world.

"Mettaton!" Undyne screamed into his metallic ear. He jerked upright, his head ringing.

"U-undyne…" A cold hand reached out and wiped away the tears on his cheek.

"Let me see that note." She took the piece of paper from him and unrumpled it as best she could. Her face fell with each word. She sat on the bed and placed the note next to her. She placed her head in her hands.

"W-what are we going to do Undyne?" Mettaton was afraid.

"There's nothing we can do." Undyne felt cold.

"That simply cannot be true! We cannot simply leave Papyrus to die!"

"Well it is! We can't put anyone in danger yet."

"You…" Mettaton stood and ran from the room.

He had made up his mind.

Soon, his voice filled the tunnels. He had invented a type of sound system to be put throughout the rooms, with help from Papyrus… Mettaton flinched at the thought of his lover.

"Everyone report to the training platform. Everyone report to the training platform." He kept the message repeating until the sparring mats were filled with monsters. Mettaton steeled his heart and stood on the dirt pile so he could be seen. The gathered monsters were muttering and whispering about why they were all gathered here.

"What's wrong Mettaton?"

"Is someone hurt?"

"Are we being attacked?"

Mettaton put a hand up to silence the crowed. He twisted his volume knob and cleared his throat. The echoing cough got the attention of everyone in the area.

"I have come to a decision. Papyrus and Sans have gone to fight the Underlord alone, and it is very unlikely either of them are going to survive." The crowed burst into scared mutterings. Undyne stormed up to Mettaton, enraged.

"What the hell do you think you're doing Robot?"

"I'm doing what needs to be done. _I'm_ not afraid of sacrificing myself for those I love." Undyne took a step back and scowled. She turned and walked away, her pony tail swaying with her steps. Monsters moved out of her way leaving a path through the crowed. Mettaton turned his attention back to the crowed. "I, Mettaton, am going after them. If anyone else is willing to follow me, I implore you to speak now. They need all the help they can get."

The crowed stood in a stunned silence before exploding into voices. Mettaton made a screeching sound to silence everyone.

"I will not ask anyone who is unwilling to risk themselves to follow me, because I know it's going to be a very dangerous mission. If anyone is willing to help me, I will be leaving the tunnels at the top of the hour, not one minute later." He turned his volume down and left, leaving the gathered monsters to talk among themselves.

Thirty seven minutes, Mettaton was standing in the kitchen of the decoy house. He was surprised to see almost a dozen other monsters had joined him, including Napstablook and Undyne. He turned to his cousin and gave him a tight hug.

"I am sorry dear cousin, but I cannot allow you to come with us." Before the other robot could object, Mettaton gave him a grim look. "I cannot allow you to get hurt… I would not be able to live with myself knowing I failed you. I cannot lose you again. Please stay here."

"B-but…" Blooky saw the tears in his cousin's eyes and sighed. "Alright Metta… please stay safe."

Mettaton smiled at his cousin and gently pushed him back to the trap door. He turned his back, afraid that if he were to watch his only other family leave, he would break down. He looked at the gathered army and smiled grimly.

"Tonight, this ends. We will no longer allow the Underlord to rule over us. We will no longer allow him to take our loved ones from us!" He got the army riled up as Undyne handed out various weapons. Swords, spears, bows and arrows, maces, clubs. There would be no mercy on this run. Mettaton pulled his hair back into a small pony tail to keep it from his face. The other monsters followed his suit, pulling fur into spikes and painting on their faces.

He bared his fangs and let his lower pair of eyes gleam. A chill ran through the air of the kitchen as the monster took in the robot about to lead them to a massacre.

"Tonight, we show them _no mercy."_

* * *

Sans lifted the Other into the air and slammed him down on the ground in front of the pile that was once his brother. He lifted the Other again and slammed him into the wall. The pile was now ash. He slammed the Other down in front of the ash pile again.

He lifted the crying Other, slamming him into the ceiling. The pile was stirring, now bones and fabric, not ash. The Other was released and slammed into the ground again. Sans felt the magic coursing through him like he never had before.

Before he always had it under control, but this… _this…_ If he had known what it was like to lose, control he would have done it ages ago. A deep chuckle escapes his mouth as his magic engulfs the Other once again.

The pile was ash again, a red cape fluttering pathetically. Sans spread his hand out and felt his mouth curl into a deadly grin as the Other Sans was spayed out in front of him, arms and legs splayed like a star in the air. He took no notice of the purple tears running down the Other's face.

The Other killed Papyrus. The pile was bone again. The bones were trying to stand up. Sans jerked his hand, causing the Other to be pulled in two different directions. Sans didn't care to notice the cry that filled the room. The pile was now ash, the grey dust being kicked around by the magic swirling through the air.

Sans felt something bubbling up. It wasn't a chuckle. He let it escape. It was maniacal giggles, chilling part of himself to the core, but it was too late… his magic had consumed any rational part of his mind.

He saw red and threw the Other into the wall hard enough to crack the stone. The red faded as he let the magic drop. The red returned when he picked the Other back up again.

Sans wanted to make him pay. _Had_ to make him pay. He _killed his brother._

"You think your whimpering and crying will convince me to spare you?" Sans never heard his own voice so cold. The Other floated above him, trembling pathetically, his indigo tears floating upwards with the gravity magic. The red surrounding the Other spiked a deeper red, a blood red.

"P-please… I didn't mean to- I never wanted to…"

"You killed him… _YOU KILLED HIM."_ Sans through the Other at a stone column, the other breaking right through it and slamming into the far wall.

"Brother…" A weak voice from behind him caused Sans to drop the red magic and turn around. His eyes landed on the pile of ash, but it wasn't a pile of ash. It was Papyrus. He was trying to stand. He got to his feet shakily and held a hand out to Sans.

His knees gave out and he tumbled to the ground. Just as he was about to hit the floor, a magenta colored magic surrounded him. Papyrus was lowered gently onto the ground.

Sans stared at him with fearful eyes. The Original took a step towards the ghost of his brother, not caring what the Other was doing behind him. Sans reached a hand out to touch his brother's cheekbone when the taller skeleton flinched away from him.

This reminded him of something… a small part of him came back to life, recalling when he first met this Papyrus and how he thought he was the Other. Sans put a hand to his eye, feeling the bitter magic lick and consume the fingers.

Pulling his hand away, he saw the dying fingers of red flames dance on his hand. Sans sucked in a breath as he realized what was happening. For the first time, Sans looked around. The lab was destroyed. Stone rubble and destroyed equipment littered the ground. There were distinct skeleton shaped indents in the stone walls.

He saw a figure moving on the corner of his eye. He turned his upper body to look, his feet cemented in place. Alphys was kneeling next to another version of himself, both looking scared and confused. It caused Sans' head to hurt. He turned back to Papyrus and let his smile drop into something horrified.

"Pap…" the red magic still flared from his left eye. Just as his brother was about to say something, there was a clamor above them. A cry rang through the room and a dozen monsters filled the destroyed room.

Leading the pack was Mettaton, but not the Mettaton Sans knew. This one was dark. This one was not going to spare anyone. He gave a quick command and the monsters rushed forward. Two of them immediately latched onto Sans' arms, pulling his away from Papyrus and holding him down. Four went over to Alphys and the Other, helping them to their feet. Two stood by the door, guarding it, and Sans guessed there must be three more by the front door.

Mettaton was helping Papyrus stand, and when Sans tried to lunge for his brother, the two monsters held him firmly. He tried to struggle, but the fading magic had taken its toll on his cracked soul. He fell limp, relying on the two to keep him upright.

Mettaton stalked over to Sans and made him lift his head with one of his arms. The look in the Robot's face gave Sans another piece of the puzzle. He thought Sans was…

"Mettaton-" Sans was cut off by Mettaton's fist swinging at his face. He had no power to dodge it, and let it hit him square in the jaw.

"I am not angry about what you did to me, but I am furious about what you did to Papyrus, what you did to Sans… You sick Bastard!" Another fist came flying at him, and Sans prepared himself for the worst. When nothing happened, Sans dared to look.

Papyrus had stuck his hand in between Mettaton's flying fist and Sans' trembling face. Both skeleton and robot looked at Papyrus with a shocked expression. Mettaton's bloodlust faded from his face the longer he looked at the taller skeleton.

"Mettaton, this is not the Sans that did this to you." Mettaton looked quickly between the two skeletons incredulously.

"B-but… he had the red magic!" Mettaton pointed threateningly at Sans, who couldn't move. Papyrus made a keening sound and let the light in his eye vanish.

"Both of my brothers have the ability to wield the red magic… when it takes over their minds and souls, they cannot fight it off. Look at his soul if you don't believe me."

Mettaton looked over at Sans, who was slumped in the grasp of the two monsters. He used his bottom set of eyes to look through the skeleton. He gasped when a familiar cracked soul came into view. It was even more broken than last time.

The black holding it together was fading, and the cracks were surrounded with an angry red, as if infected. Mettaton pulled back and felt tears in his eyes. He, the one who came to save them, almost… Mettaton felt sick to his stomach. A voice from the other side of the room called their attention.

"I…um… t-think I can explain… at least a little…" Dr. Alphys seemed back to normal, or at least back to the way Sans remembered her. She adjusted her cracked glasses and shuffled her feet. "Now that I'm… um… back in my own head… for now at least."

"Alphys… why did you hurt Undyne?" Sans' voice was monotone, but he needed to make sure she was really back to normal. The little reptile covered her face and sobbed a little.

"I… I never wanted to hurt her… b-but I couldn't c-control it… his r-rage was controlling me too…"

Sans had a hunch it was something like that. Maybe this is why Gaster sent him here. _Destroy hate_ he had told the skeleton. Maybe he was here to save them? To save… Sans? Another voice joined in.

"Oh no… not again. I did it again, didn't I Alphy?" It sounded exactly like himself, but more timid. More afraid.

The Other Sans looked around the destroyed lab with watery blue tears in his eyes.

* * *

 **Sorry to cut it off here guys! I was planning on going farther, but I wanted to leave** ** _something_** **for the next chapter!**

 **Next chapter is going to be the background for Other Sans' powers, and maybe even the last chapter… why knows! All I** ** _do_** **know it that almost everything is going to be explained in the next chapter.**

 **Thanks for all the follows, favorites and reviews. It means to much to me knowing people enjoy what I write.**

 **Also if anyone was confused about what happened during the 'dunking', the Sans' magic color was slowly switching. Red turning purple, then blue at the end. Blue turning magenta, then blood red. I really wanted to show Sans losing control without out straight up saying 'hey this is what is happening right now', and the whole thing with the pile of ash/pile of bones thing was because since Sans was losing control, his own memories of the genocide run were being confused with reality.**

 **If anyone if confused about the characters or anything else, shoot me a message and I'll be happy to clear things up for you!**

 **Until next time!**

 **~Starlight**


	8. Chapter 8

"P-papyrus? Are you okay?" The Other Sans sounded meek and scared, as if he was expecting to be hit at any moment. Papyrus left Mettaton's embrace and went over to his brother. The smaller skeleton was looking at the taller as if looking at a ghost.

"I am alright Brother. I am glad to see you back to normal." Other Sans ran and embraced his brother, sobbing into his shoulder. Everyone watched the reunion with mixed feelings of adoration and confusion.

"Alphys…" The Original Sans addressed the small lizard. Both Alphys and Undyne's heads turned to look at him. "You said you could enlighten us a little?"

"O-oh um… yeah. It started when Sans was a child. His powers were too strong, o-often taking over his personality a-and causing trouble." Alphys looked over at the Other with a sad smile. He returned it shakily, picking up the story.

"I can't really control it… I honestly don't know how long I have until it takes over again. I… I don't want to hurt anyone again." The Other Sans let a few blue tear leak from his eyes.

"Brother, we are here to stop this from happening again." Papyrus walked over to the Original Sans, helping his steady the smaller skeleton.

"There's nothing you can do!" Other Sans shouted, obviously getting hysterical. "I'm a lost cause! I asked you last time Papyrus, but you didn't listen. This time… please. Please just kill me."

The room was blanketed in a shocked silence.

"Sans, you can't-"

"I can't what? If I live, it'll take over again, and I'll hurt you again…" Original Sans felt his soul ache for his double.

"Well…" Thankfully Mettaton still had his head together. "Why don't we go back to the base and talk about this. Making hasty decisions leads to bad consequences."

"We can't take him," Undyne gestured to Other Sans. "Back to the base. It's built to _fight_ him, not invite him back to a cup of tea!"

"I can take a short cut right to one of the rooms, so he won't see anything." Sans felt weird talking about himself in the third person, but his idea was still the best anyone had. Undyne hesitated, weighting her options. She looked around at the rag tag group gathered in the ruined lab and sighed, her shoulders slumping.

"Looks like we don't have any more options… Just keep him detained." It was obvious she wanted to strangle the Other Sans, but she couldn't bring herself to harm a monster that was sniffling like a child.

"T-thank you Undyne-"

"Don't talk to me. We still hate you." She turned and snapped at Other Sans, causing him to shrink back into Other Papyrus' arms. Alphys placed a scaly hand on Undyne's arm to try to comfort her, but the latter moved away, not trusting the scientist just yet.

Original Sans held a hand out for his double, who placed a shaking hand on top. In a flash, Both Sans' were in the conference room at the base. Sans figured this would be the best place to hold Other Sans and still have the room to make decisions.

The Other Sans sat in one of the chairs and looked down at his hands, almost like a child preparing themselves to be scolded by a parent.

"I'm sorry…" Other Sans barely whispered.

"I know, but they might not be as forgiving."

"How are you here?"

"I was sent by someone to fix this timeline." Sans wasn't sure how much he wanted to tell this monster.

"Someone? Do you know who?"

"Does the name 'Gaster' mean anything to you?" Sans knew his answer instantly. Other Sans' eye lights grew bright with shock, and he sunk into his chair. It was strange to see those sharp fans behind a trembling mouth, Sans thought.

"G-gaster? He sent you here? Is… is _he_ here?"

"No, but he's been guiding me, I guess." The Other Sans suddenly seemed even more terrified of the Original Sans.

"Did h-he… do it to you too?"

"It?" Sans needed to get some real answers out of this clown before the others made it back.

"It! _It!_ The experiments… the t-tests." Other Sans' started shaking, his black jacket sleeves being pulled and picked at nervously. The puzzle pieces were starting to fall into place for Sans. Experiments… yeah Sans knew all about experiments.

"Yeah, but I'm guessing yours didn't go as well as mine." Sans eyed his double, watching for changes in demeanor, looking for clues.

"They started when I was a child… I did it to protect Papyrus but I couldn't hold it all in. He kept putting that liquid in me, but I couldn't control it… it took over again and again." Purple tinted tears flowed over Other Sans' face, causing Original Sans' chest to clench in fear. It was starting to take over again.

"He didn't start my tests until I was working under him…" He had a good idea why, but he didn't want to believe it.

"He knew what not to do with you then. I was his… his… his _fuck up child!"_ Other Sans' eyes glowed red with anger. He slammed his fist down on the table, causing a crack to spread through the wood. _"He fucked me over and left me for dead! Left me to hurt Papyrus!_ _ **He fucking left me!"**_

"Calm down!" Sans yelled at the Other, trying to get his attention through his rage. Other Sans blinked and let his eyes fade to a dark blue. He looked away, ashamed.

"I'm sorry… I'm s-sorry…"

"It's fine." Sans sighed and sat down opposite of Other Sans. "It seems like we're on more even footing than I thought we would be."

"What happened?" Original Sans raised an eyebrow at Other Sans, asking him to elaborate. Other Sans messed with the zipper of his black jacket, the one that was oh so similar to Sans', but it was just a reminder of how different they were. "What… sent you here?"

"I'm not sure… but you might know better than anyone else here. Is there someone in this timeline that can… mess with time? Or, erm… reset the timeline?" Sans wasn't sure how to explain it to someone who might not know what he was talking about. Other Sans' eye sockets widened with recognition.

"Yeah! There was one but…." Other Sans looked away, his facial features looking troubled. "But I lost track of them after it took control again. I don't know if they're even alive anymore." Sans sighed and propped his chin up with his fist, looking over Other Sans' right shoulder.

"Well, if it'll make you feel any better, the human is in the compound. They're alive and well. My kid can do the same thing, essentially. After a long and happy timeline, they decided to fuck around and reset." Sans hadn't meant to let his bitterness seep into his explanation, but he couldn't help it. He wouldn't be in this situation if the kid had just stayed where they were. "When the timelines reset, I watch the moments flow backwards and write down any anomalies – for future reference.

"Well, with this last reset, something changed. I didn't know who it was at first, cuz it just seemed like a wall of shadows, but he managed to take some half form. He dripped this… black goop into the timeline, contaminating it. He told me to erase the hate, but I don't know what he meant… at least at first.

"But now I think I know what he wanted me to do. All throughout this nightmare, I've had feelings in my chest, pushing me towards one direction or the other, helping me make the right choices. I think he's trying to get me to make amends for what he did.

"Gaster is trying to save you." Sans finished, finally looking Other Sans in the eye. The Other's eyes grew wide with fear and hope, and odd combination in Sans' opinion.

"S-save me? But how?" He sounded frantic, but Original Sans figured he would also be frantic, if put in his double's place.

"I don't know… I guess he figured I would find… something." Both Sans' slumped in their chairs, not liking their predicament. They heard a sudden commotion outside the room and knew the rescue party had returned. With a sinking feeling in his gut, he hoped things wouldn't end in bloodshed.

The door burst open, Undyne in the lead, followed by Mettaton, Papyrus, Aphys and the small monster with large ears and scarf. The others must have gone off to rest.

"Have you found anything out?" Undyne addressed Sans, but was looking anywhere but the two identical skeletons.

"Um… that he isn't actually a bad guy?" He wasn't sure how much about Gaster and the timelines he wanted to share with the others. Undyne snorted in disbelief and turned her attention to Other Sans, who cowered in his chair.

"And what do you have to say about this, _Underlord Sans?"_ She said with enough spite to break a bone. He cowered even more, fidgeting with his sleeves and sweating.

"I don't… I didn't mean…" He started tearing up again, and Original Sans felt pity for his double.

"It wasn't his fault." Original Sans spoke up again, drawing attention from the Other. "He did it because of the experiments." Other Sans looked at him incredulously, not knowing his was going to spill everything right then and there.

"Experiments? Brother, what is he talking about?" Papyrus addressed his real brother, still obviously nervous around him. If it weren't an insanely tense situation, Sans would have made a pun about being afraid of the trembling sack of bones in front of them,

"If this timeline is the same as mine, no one will remember him, but Gaster did some nasty experiments on him- us. So nasty, it caused his powers to lose control and take over."

"B-brother… is that true?" Papyrus seemed almost afraid to hear the answer. Other Sans just nodded and let his eye lights dim at the following gasps of disbelief. Original Sans remembered one of the more terrifying tests Gaster ran on him.

 _He was tied down to a table, not able to move a muscle. Gaster had injected him with some clear liquid that caused him to become temporarily paralyzed._

 _Gaster walked towards Sans, his smile faltering as he saw the fear so plainly etched into Sans' face._

 _"Do not worry." He said in his strange way. The words were clear to Sans, but only because he had worked so closely to the doctor for many years. "It will be over very soon. Please, just bear with me." He injected something into Sans' upper arm, and the pain instantly started._

 _Sans' back arched off the table as far as the restraints would let him. He screamed so loud he dislocated his jaw bone, but there was nothing he could do to fix it. The screaming continued, but it was distorted, streaming through his gaping mouth._

 _It felt like he was on fire. The fire was consuming every inch of his being. He felt the fire touch his soul, and he wished he would pass out. The fire filled his soul, almost bleaching it. His soul had always been deep blue, just like his brother's, but this fire filled his heart and turned it an icy blue._

 _The fire worked its way to his skull, and Sans wished for death. He wished more than anything that he could just die._

 _The fire nestled in his left eye socket, curling around his skull. Sans found himself in a battle of wills. The fire wanted to take control, to rule over his body, but Sans had someone he had to take care of. He thought of Papyrus, his smile, his laugh, and fought against the fire._

 _The fire fought back harder, pushing Sans' will, trying to bend it. Trying to break it. But Sans couldn't let it take over._

 _With a final scream, the pain faded, the fire diminishing to a dull ache in his eye socket. His vision cleared to see a beaming Gaster. The doctor's slim hands rested on Sans' jaw and swiftly jerked it back into place, but that pain was nothing compared to what he just experienced._

 _Gasping for breath, Sans felt the bonds release his limbs, and he collapsed into Gaster's arms. He felt something wet drip into the back of his skull. Sans looked up and saw tears dripping from the Doctor's grinning face._

Sans came back to the moment only to see everyone staring at him. He felt a faint pricking on his skull and reached a hand up to his eye. The flames had reached down the back of his head, almost licking the back of his neck. Sans calmed his breathing, letting the flames disappear back into his left eye socket.

"Brother…" Papyrus tried getting his attention, but Sans was too focused on the memory. No wonder Other Sans lost the battle. He had almost lost the battle too. Sans looked at the Other, this time with more understanding this time.

"Don't pity us." Sans' voice was deep with emotion. "Don't pity what he is, what I might have been… we couldn't help what we've become…"

"Sans! Explain what you're driveling on about." Undyne slammed her fist on the table, causing the crack to grow more. Original Sans whipped his head towards the fish monster, no emotion in his face.

"What we've been through… you would have given up Undyne. You never would have been able to survive what we survived. A weaker monster would have dropped dead, but we were strong enough- to live at least. And now…" Sans laughed, but it was dark and insane sounding. "Now, I have to figure out a way to fix this, or I'll be trapped here forever!"

"Fix what, dear?" Mettaton finally spoke up, no longer pumped on adrenaline and bloodlust. He sounded tired and resigned, but also cautious and worried.

"This!" Sans gestured at Other, his own hand shaking violently. "Whatever the Doc did to him messed with his head and his magic. He wants me t-to fix his screw up, and even then I don't know if I'll ever make it home! If I'll ever see my friends again. If I'll ever see _my_ Paps again…" The dam broke, and Sans let out a breathy sob. It was all too much for him, being captured and tortured, living through the memory, realizing he may never see Papyrus ever again.

A hand came down on his shoulder, and he flinched away so violently he almost fell into to the ground had another set of arms not caught him at the last second. Papyrus was standing to his right, arm outstretched to shoulder height, looking shocked. Mettaton was on his left, all four arms helping to right the skeleton. Undyne watched the whole scene with mixed emotions before making a decision. She waited until Sans was standing on his own two feet before speaking.

"Everyone seems like they're about to pass out on my floors. Let's break for the night and meet again after breakfast. You," She pointed a spear at Other Sans, who flinched away. "You're going to stay in this room. You are not going to leave unless blindfolded and guarded. Everyone else, dismissed." She left the room first, followed closely by Alphys. A small part of Sans' mind commented that the two of them weren't going to sleep as much as talk through the night.

Other Sans looked sadly at the door, watching the monsters leave. Mettaton laid a hand on Papyrus' shoulder and whispered something in his ear. The skeleton hesitated before nodding and whispering back.

Papyrus came over to Sans and picked him up like a sack of poptatos, just like back home. Sans let himself relax in his brother's arms. Let himself believe it was just Papyrus carrying him home after a night drinking at Grillby's, but when he was placed down on a bed that was most definitely not his own, Sans was brought back to the present.

He was in a strange timeline, with a mission that might actually be entirely impossible, and no promise of a return home after completing said impossible task, no way of knowing if he would ever see the one person who mattered to him again.

Sans let the tears roll down his skull as the door clicked shut, leaving him alone in the dark, musty room.

Sans wished he could wake up from this nightmare. He wished he could either wake up in his home, or not wake up at all.

* * *

Sans watched at the last monster walked out of the large room. The door clicked shut behind his brother and his double, leaving him in almost complete darkness. There was a little light coming from the balls of magic along the ceiling, but that only helped to cast eerie shadows.

He gave a shaky laugh, the situation finally sinking in. He was free of his magic only to be made a prisoner in this room. The irony was not lost on him. Sans let the hot tears roll down his face, but laughed again at their blue tint.

It had been so long since he had seen his real soul color…

There was noise at the door. Sans couldn't make out any words, but it sounded like a whispered argument. He hoped it would be settled soon so he could fall asleep, but the door opened a crack. The sudden light made him flinch and squint.

A tall figure slipped into the room, but Sans could only make it out after the door closed and his eye – adjusted to the dark – were finally able to identify who it was. Papyrus had come back, carrying something large.

"Brother… I couldn't just leave you in this room… I am I sure I will get quite the scolding come morning but…" He trailed off before handing his load to Sans. The shorter skeleton was surprised to feel soft fabric beneath his fingers.

He was holding two pillows and a large, full blanket. Sans felt his soul tremble at the gesture, and he too knew Papyrus would get in trouble for being so nice.

"Why…?" His voice was as weak at the lighting. Papyrus' face twisted in confusion.

"Because you are my brother, Sans. Nothing will change that." Papyrus turned to leave before hesitating and pulling Sans into a tight hug. "I've missed you so much brother." His usually calm voice cracked, causing Sans to lose all composure.

"Thank you…" Sans choked out though his tears. Papyrus nodded and turned to leave. As he came to the door, Sans spoke again. "I never stopped loving you little bro."

Papyrus hunched his shoulders and let out a shuttering laugh before opening the door and leaving Sans in darkness once more. Sans set up the pillows and blanket to form a makeshift bed and settled in. He realized these must have been from Papyrus' own bed, because the fabric smelt of home, of better times.

Sans smiled and buried his face in the pillow, no longer crying.

* * *

 **So this isn't the last chapter… shocker. I kind of lost where I was going with it halfway through and realized I liked the angsty exposition more.**

 **I always miscalculate how many chapters are going to be in a story, but I would estimate another chapter or two and maybe an epilogue.**

 **I'm very sorry for taking so long to update this, but I've been working very hard on my other Undertale story,** **Love yourself.** **It's a collection of oneshots dealing with self-harm, eating disorders, depression, suicidal thoughts and other mental problems, and having Sans help you cope. I've been really busy because I've had a ton of requests for different situations, so if you think it might help you, go and read some of the chapters and drop a request or two.**

 **Thank you everyone for reading and reviewing and supporting me through this adventure! It'll be a shame to wrap this up, but all good things come to an end.**

 **Until next time!  
~Starlight **


	9. Chapter 9

_Sans was standing in a dark room. Looking around, it reminded him of the in-between where he would watch the timelines reset, but it wasn't quite the same. The shadows danced along the invisible walls. They danced and writhed, almost as if they were alive._

 _He reached out a hand to touch the shadow, afraid that it'll be real but just as afraid that it won't be. His fingers dipped into the darkness, just barely. The darkness reared back and plopped onto the ground, like oil dripping from a pipe._

 _The shadow solidified into not a person, but a shape. A shape with a timid smile and cracked eyes._

 _"Gaster?" Sans didn't speak out loud, but his words danced through the air, as if he could speak aloud with his mind. The shadow man perked up, his timid smile growing a little. The shadow – Gaster – bounced up and down in excitement, like a toddler._

 _"What do you want me to do?" Sans' thoughts spoke aloud again. Gaster's dripping shadow form pulled itself up, as if straightening his back from a slouch._

 _"Sans. I'm glad I can talk to you this way." His smile never moved, but a mature voice flowed through the area._

 _"What's going on?"_

 _"How is your soul doing Sans?" Gaster spoke to him, blatantly ignoring his question. The short skeleton looked at the figure in shock. He hadn't thought of it. He pulled the small heart from his chest and held it out for Gaster to see._

 _A white hand appeared from the shadows and cradled the heart. The face never changed, but the air around them did._

 _"You need rest, Sans. I did all I could do when you were awake, but I cannot keep patching you up from the void." Gaster made the soul glow bright, and Sans had to glance away. When the glow faded, it looked good as new._

 _Sans had to take a closer took to see the faint cracked lines spreading through it. It reminded him more of scars than actual cracks. When he let the heart sink back into his chest, Sans felt better. His shoulders felt lighter and the weight on his chest seemed lighter._

 _"Now Sans. We must talk about what to do in this world of yours." Gaster's form was starting to liquefy again._

 _"What do you want me to do? How am I supposed to save this other me?" Sans felt his desperation bleed into his words, but he felt he was trapped with no escape. Gaster looked at him with empty eyes, no expression._

 _"I know I messed up Sans. I know what I did was wrong, but that's why I need you. I need you to right my wrongs."_

 _"But_ how _?" Sans needed some guidance._

 _"I… am unsure."_

 _"What?"_

 _"I do have one idea, but it is not ideal."_

 _"It's better than what I have. Tell me what you're thinking Gaster."_

 _"You have to kill him." Gaster's words were remorseful._

 _"Kill him? What about saving him?" Sans was horrified._

 _"Kill him and take the hate from him and then reset. Everything will be fixed. Everyone will be set free." Gaster's form was melting more and more. "I don't have much longer here. Please Sans. Fix my mistakes."_

 _"I can't kill him! I'd be killing myself. I can't do that to his Papyrus…"_

 _"Please Sans…" The shadows collapsed into a puddle before dispersing, leaving Sans alone in the room._

* * *

With a gasp, Sans woke up and almost fell out of bed. That dream… Was that really Gaster? He shook his head, trying to clear his thoughts.

"Brother? Breakfast is being served, and I thought you would like to eat something. I… honestly don't remember seeing you eat anything since we found each other, which is worrying." Papyrus poked his head into the room. Sans was pleasantly surprised to see the concern on his scarred skull.

"Thanks Pap. I'll be right out."

"Did you have a nightmare too?" Papyrus spoke softly from the door, causing Sans to jerk his head in shock. The shorter skeleton hopped off the bed and laced up his sneakers before meeting the taller by the door.

"Yeah, um, sort of." Sans smiled guiltily and chuckled.

"Do you wish to talk about it?" Papyrus placed a hand on Sans' shoulder, his black glove standing out against the ratty fabric of the jacket. The thought of telling Papyrus about what he had to do to his real brother made Sans feel sick.

"NO!" He snapped, and instantly realized his mistake when Papyrus made the sound of a kick child. "I m-mean, I'm not really in the mood to talk Pappy…"

Papyrus didn't respond, instead just started walking to the lower levels. Sans followed guiltily. They made their way to a room Sans had never seen before. It was on the bottom level, hear the training pit, and was twice the size of the meeting room.

It looked like a standard cafeteria, with rows of tables and a kitchen of sorts. Various monsters were scattered at various tables, talking quietly to each other. Papyrus walked right to the kitchen, and Sans almost ran to keep up with Pap's long strides.

"G-grillby?" Sans almost choked when he got up to the counter. There he was, but it wasn't him. Instead of a soft orange, his flames were violently crackling blue. He turned to look at the shorter skeleton and snarled.

"Oh great. I heard there was a copy running around here." His sharp mouth curled into a sneer. Sans was frozen in shock, not used to being spoken to by the fire monster, let alone such bitter words. Grillby just sneered again at his silence and threw some food on a plate before unceremoniously tossing it in front of Sans.

Even Papyrus seemed shocked, but didn't mention it until they got to an empty table.

"He usually doesn't talk to us…" Papyrus muttered into a forkful of food. Sans just sat there, staring at his plate. He didn't respond, or acknowledge that his brother said anything. "Brother, are you alright?"

Sans opened his mouth to say something, but nothing came out. A tear worked his way down his cheek as he stared blankly at his plate.

"Brother! Are you hurt?" Papyrus was starting to really worry about this Sans. Sans just shook his head.

"Grillby was my best friend, next to Pap. He always listened to me, and always teased me about my tab but never really cared if I paid it back or not. He would… w-walk me home if I got drunk at the bar, a-and…" The tears kept falling, but he didn't want to talk about the nights he and Grillby spent together. Seeing such a monster with the face of his friend… it hurt.

"He wasn't always like this. He used to run a respectable business. Had a lot of friends. Had a family. But… it was all destroyed. He hardened, and became bitter. You cannot blame him." Papyrus put down his fork. Sans looked at his plate some more, not sure how to feel about this all.

"Papyrus… If I had to do something awful, but it fixed everything… would you hate me?" Sans was afraid of his answer. The taller skeleton stared at the smaller.

"Brother, what is this about?"

"Please don't hate me…" Sans whispered to himself more than to Papyrus, but the taller skeleton heard anyway.

"Sans please. What is going on?"

"It's nothing bro." Sans' eyes were blank, dark. He stood, forgetting to eat. He could feel the fatigue in his bones from the lack of food, but he knew deep down this would all be over soon. He left the cafeteria, his feet moving on their own. He ignored the calls after him and made a bee line to the conference room.

Papyrus followed behind, afraid something was about to go seriously wrong.

* * *

Other Sans was just waking up, the scent of his brother and the warmth of his kindness gently surrounding him. He couldn't remember the last time he was this happy. He sat up with one of the first genuine smiles in a long time and rubbed a sleepy eye.

The door creaked open. Thinking it was Papyrus, Sans sat up and looked over, but the figure was hidden by shadows. Sans stood up and stretched, cracking his back and letting his smile grow a little. He hadn't gotten a good night's sleep in many years.

Realizing he still had all the blankets around his feet, Sans guiltily began gathering them up, trying to fold them.

"I'm sorry Papyrus. I'll get this cleaned up before anyone sees."

"I'm sorry Sans." It wasn't Papyrus. It was the other Sans, the one in the blue. Sans felt something in his soul, but he didn't know what. Apprehension maybe?

"Oh, s-sorry. I thought you were… wait, why are you sorry?" Sans was still trying to fold the blankets, but it wasn't working out. A blue aura picked the fabric from his fingers and folded them perfectly. Shocked, Sans smiled and turned to the Other Sans to thank him.

His smile faded when he saw the grin look partially hidden behind a blue hood.

"You gotta understand." He walked closed to his double.

"You're scaring me…"

"I don't have any other ideas."

"Listen, I don't know what you're planning but-"

"Gaster told me this was the best way." Sans, the original Sans, took a final step towards Other, who realized this wasn't some friendly visit. Other Sans took a fearful step back, sweat beading up on his forehead.

Other Sans was wrapped in the same aura as the blankets, freezing him in place. Neither skeletons noticed the door creak open and close again. Papyrus sneaked in, unnoticed by either of the Sans'. His plan was only to interfere if things looked grim. He was taught to let others deal with their own problems, but this was his brother…

"I don't want to do this." Original Sans said with a slight tremor.

"D-do what? Please… what are you doing?" Other Sans tried to struggle, but he was stuck in place.

"I… Please don't make this any harder than it has to be." The magic around Other Sans tightened, causing him to struggle more. Sans relaxed his wrist and was about to give it a final flick when another aura filled the room.

Other Sans' wasn't red anymore, but it was a darker blue than original Sans. The darker blue surrounded the Other Sans, somehow breaking the Original Sans' magic.

Sans summoned his blasters and let them charge with a single point. Other dodged, just barely. It was obvious his teleporting powers were rocky at the moment. Sans teleported directly behind Other and aimed a bone at the back of his skull, but Other must have sensed him and dropped to this knees, knocking Sans' feet out from under him.

Falling hard, Sans felt his bones jar, but he didn't have time to call out because a bone dug into the ground right next to his face an instant later. He rolled over and teleported away from Other, who was getting more and more confident with his magic attacks.

Other swung an arm, dark blue bones following in his wake. Sans barely managed to dodge, the pace of the fight starting to pick up.

Dodge, roll, dodge. Throw, shoot, dodge again.

Sans felt himself start to slip up. Who knew it would be this hard to fight himself. He shot his blaster again, but Other rolled to the side, sliding on his side as he shot another bone. Sans summoned a wall of bones, right where Other was about to land.

Just as Other was about to slam into the bone wall, he blipped out of the air, landing several feet to the left. Other blinked, shocked he managed to teleport.

Sans felt his soul shutter at the effort of fighting, but he knew this was what needed to be done. He couldn't initiate a fight sequence, because a monster soul can't be taken out of the host like a human's.

Sans felt his leg freeze in place and looked down, his foot surrounded by dark blue. Since it was such a small, concentrated area, the magic was a thousand times stronger. Sans threw his own magic at it, but he couldn't budge it. He tried teleporting, but the magic held him in place.

A bone came hurling at his face, and Sans simply closed his eyes, waiting for the impact. When none came, he hesitantly looked. The bone was surrounded by an even darker blue magic. Both Sans' turned to see Papyrus standing by the door, one hand outstretched and a devastated look on his face.

The magic holding Sans' foot in place disappeared, causing him to fall backwards. In his desperation to stay upright, Sans shot a blaster with an accidental wave of the hand. Both Sans' cried out.

The magic blast went straight for the skeleton, incinerating him in an instant. Sans started at the pile of ash in shock and horror. His emotions drained from his bodies, the blasters disappearing slowly. Staring at the pile of ash that used to be a living, breathing monster.

Other Sans stared at shock at the pile of ash that used to be his brother. The rage he had been fighting against for so many years reared its ugly head, but he felt dead. There was no use fighting when his brother was gone. Other Sans turned to look at his double, who was staring with complete horror at the monstrosity he just committed.

"No, no, no, no, no, no, NO. NO. NO! NO! NO! PAPYRUS NO! PLEASE OH GOD PAPYRUS!" He rushed to the pile of dust, sobbing. Other Sans watched shocked, as his brother's killed sobbed into the blood red cape covered in ash. "Not again… oh god please not again…"

Other Sans wanted to fight. Wanted to avenge his brother, but…

"What were you trying to do?" He spoke softly, tears threatening to spill over.

"I needed to kill you. If I killed you, I could absorbed whatever screwed you over, and reset. Everything was going to be fine…" he was babbling, sobbing hysterically.

"Do it." Other Sans was almost silent. Original Sans blinked in shock.

"W-what?"

"Do it. Kill me. Let me be with my brother… please." Other Sans dropped his head, waiting for the fatal hit.

"I'm so sorry…" Original Sans stood, eye sockets blank and emotionless. The door slammed open, startling the two skeletons. Undyne barreled through the door frame, only stopping when she kick the pile. Looking down at her shoe, her one eye opened wide.

"W-what?" She looked up and saw both Sans', sweating and crying.

"I'm sorry Undyne." Original Sans placed a hand on his own jaw bone, or rather, his double's jaw bone. His other hand reached around and rested on the back of Other's skull. With a soft look and a whispered goodbye, Sans snapped his neck, separating the skull from the spine.

Undyne gave a roar of fury and rushed at him, but with a single deft motion, Sans froze her. Sans stared down at the sad smile on his double's face as his body fell to its knees. Other's head went first, the dust sifting through Sans' fingers. His shoulders went next, slowly falling onto the ground.

Sans fell to his own knees, ignoring Undyne's struggling. As the Other turned to dust, inch by inch, his soul appeared. Sans reached a trembling hand out to hold the dying soul, its dark blue greying quickly.

As the blue faded, an inky blackness began to seep from the bottom. It pooled in Sans' palm, burning the bones painfully. As the last of the blue faded, the heart shattered, leaving the pool in his hand, swirling on its own.

Sans wasn't sure what to do, now that he could feel his LOVE increase. His health expand, his EXP growing. It made him feel sick, because it means he became the real monster. He didn't bother hiding the tears as they flowed from his eye sockets.

A sob ripped through his body, shaking him violently. A blue tear dripped into the shadows pooled into his palm. It was instantly absorbed into the darkness. Remembering what Gaster said, Sans had an idea.

He summoned his own soul, the scarred thing that it was. He held the little heart in one hand and the shadows in the other.

 _Absorb the hatred_ Gaster had said. Sans brought the soul to the shadows, and let the blackness seep into the blue. Pain was the first thing Sans noticed. The more the black etched into his soul, the more he wished for it to end.

It pushed the blueness back, turning it grey first, then fully taking over. Sans' felt his magic rebel at the intrusion of the darkness, but he held strong. He needed to right this wrong.

Sans dropped his hands, both empty. The black soul found its way back into Sans' chest, burying itself deep in his being. He chuckled humorlessly and slipped off his jacket, pulling on the black jacket instead. A tribute to the souls he destroyed.

He began to sway, and finally collapsed.

* * *

 _It was a creature he had never seen before. Tall, so many arms with so many claws. It tried to capture him, but he refused to be held down. Sans fought back, refusing to give up._

 _It grabbed at him, wrapping its inky fingers around his waist. Sans felt overwhelmed. His instincts screamed at him to give in. Let the darkness take over._

 _It would be okay, the darkness whispered to him. Give in, and I'll make the pain stop._

 _Sans fought back. The creature reared back, not used to this. The last one gave in so easily._

 _Sans fought back. He made the creature retreat just a step. He thought of his Papyrus._

 _Sans fought back. The creature keened loudly. He thought of the other Papyrus, dusted._

 _Sans fought back. The creature tried in vain to get a hold of him. He thought of the other him._

 _Sans fought back, and the creature shrunk until it was the size of a snail. It tried to run away, but Sans was done fighting. He walked over to the dark blob._

 _And stepped on it._

* * *

"…? Brother? Please wake up! Oh gee… Undyne nothing is working!"

Sans came back to his senses very slowly. The first sense to come back was sound, a loud and distressed voice boomed through his skull. The second, touch. He was in a bed, with scratchy covers and no sheets. The third sense was smell, of dirty socks and cooking spices.

His vision came back last. He saw a bare ceiling first. Turning his head to the side used almost all his strength, but what he saw shocked him.

A dresser with a lamp. A treadmill. A pile of socks. A tornado.

He was home. He was finally home, and that means…

"P-PAPYRUS!" He hadn't meant to scream, but he couldn't help it. Footsteps came pounding up the stairs and to the end of the hallway. His door was thrown open by a bedraggled looking skeleton. As soon as the brothers made eye contact, they threw themselves at each other.

Well, Papyrus threw himself at Sans. It took all of the smaller skeleton's strength just to sit up.

"Brother, it's been days! I was so worried you would never wake up." Papyrus cried out, a happy grin across his whole face. Sans didn't say anything. He just took in the sight of his happy, _alive_ brother. A shaking hand reached out, stroking the bone beneath his eye, the intact bone.

Sans traced Papyrus' face, every bone, every angle, as if trying to memorize it. Sans finally realized he was crying.

"Oh Pap… Papyrus." Sans threw his arms around his brother, holding on tightly. "I thought you were gone… I killed you… you- you're back though. It's fine. Everything is going to be fine now." Sans started laughing through his tears.

"You what? Sans, you never did anything to me, other than give me quite the fright! Imagine how I felt, trying to wake you up but getting no response. You'll never guess what happened, brother. I met a human! And they wanted to be my friend! Someone out there really must be looking after me." He grinned wide.

"You met the kid?" Sans asked, almost trance like.

"Yes! The Great Papyrus was going to capture them at first, but I just couldn't! They were too nice! They met all of my standards!" Papyrus posed, almost falling off the edge of the bed. Sans couldn't help but grin.

Everything was back to normal. Papyrus was okay, the human was back. He was back. Everything was perfect.

"Oh, why don't I go and get them! I've been telling them all about you brother!" Papyrus dashed from the room. Sans pushed himself off the bed and swung his legs over the edge. He looked down at his hands and felt his head spin.

He was wearing the black jacket still. That means…

The room grew dark, the shadows all coming together to block out any light. No figure formed, but a voice rang thought the darkness.

 _"Thank you…"_

Just as quickly as it came, everything went back to normal. Sans was left sitting on his bed, staring at his hands and crying, a large smile on his face. Papyrus came bumbling into the room with a small figure following behind him.

"See brother! It's-" Papyrus stopped and noticed the predicament his brother was in. "Um, Sans? Are you alright?" Sans just chuckled and looked at him.

"I had a bad dream bro, but everything's fine now." He turned to greet the kid, who ran and gave him a huge hug. Pulling away, Sans saw recognition in their eyes. "Yeah, everything's fine now."

* * *

 **That is the end of Purify the Timelines! Although I do love the dictator Papyrus and emotionally unstable Sans idea, I wanted to shake things up a bit.**

 **Thank you everyone who supported this! It's a sad occasion, wrapping up a story you worked so hard on, but also a happy one.**

 **So until next time!**

 **~Starlight**


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